Measuring head for air micrometer

ABSTRACT

The present invention aims to provide a measuring head for an air micrometer which is capable of measuring an amount of eccentricity between a main spindle and a bush hole. To this end, a measuring head ( 41 ) is configured, for example, to include a measuring-head body portion ( 42 ) and a measuring-head tip portion ( 43 ), in which: a first measurement air nozzle ( 51 A) and a second measurement air nozzle ( 51 B) are each formed in the measuring-head tip portion to extend in a radial direction of the measuring-head tip portion, and also formed to have an angle of 180 degrees with respect to each other in a circumferential direction of the measuring-head tip portion; individual measurement air supply passages corresponding to the respective measurement air nozzles (a supply passage constituted of first measurement air supply passages ( 53 A,  55 A,  63 A) and a hose ( 64 A) as well as a supply passage constituted of first measurement air supply passages ( 53 B,  55 B,  63 B) and a hose ( 64 B)) are formed in the measuring-head body portion; and measurement air is supplied to the measurement air nozzles from the individual measurement air supply passages, respectively.

TECHNICAL FIELD

The present invention relates to a measuring head for an air micrometer.

BACKGROUND ART

Consider a case where, for example, a long drilling tool is attached toa main spindle of a machine tool, and a hole, such as a crank hole or aspool hole, which requires a strict coaxiality, is formed in aworkpiece, such as a cylinder block or a valve body of an engine, by useof the drilling tool. In such a case, a bush is used for suppressing thevibration of the drilling tool. In the case of using a bush, thedrilling tool is inserted into a bush hole with the axis of the mainspindle (namely, the axis of the drilling tool) caused to coincide withthe axis of the bush hole (see Part (a) of FIG. 1, the detail of whichwill be described later).

However, misalignment (eccentricity) sometimes occurs between the axisof the main spindle and the axis of the bush hole because of thermaldeformation of the machine tool, and the like. If the drilling processis continued under such eccentric condition, the inner peripheralsurface of the bush hole is unevenly worn. As a result, the bush failsto function properly, leading to degradation in the coaxiality of themachined hole.

Accordingly, the uneven wear of the bush hole needs to be prevented inthe following manner. The amount of eccentricity between the mainspindle and the bush hole is measured on a regular basis, and theposition of the ma in spindle is controlled in accordance with theamount of eccentricity (that is, the relative position between the mainspindle and the bush hole is corrected). Thereby, the axis of the mainspindle (the drilling tool) and the axis of the bush hole are caused tocoincide with each other.

In order to achieve this, a touch sensor has conventionally been used tomeasure the amount of eccentricity between a main spindle and a bushhole. Part (a) of FIG. 21 is a side view of a touch sensor, and Part (b)of FIG. 21 is a view in the direction of the arrow W in Part (a) of FIG.21. As shown in these figures, a touch sensor 1 includes a measuringhead 2 and a stylus 3 protruding on the tip of the measuring head 2. Themeasuring head 2 is attached to a main spindle 4 of a machine tool inplace of a drilling tool. Thereafter, the main spindle 4 is operated tobring a stylus ball 3 a on the tip of the stylus 3 into contact with theinner peripheral surface of a bush hole (illustration of which isomitted), whereby the amount of eccentricity between the main spindle 4and the bush hole is measured.

However, the conventional touch sensor has the following problemsbecause it is a contact sensor, and so on.

(1) A measurement error is likely to occur because of the biting offoreign matter, such as a chip, attached to the inner peripheral surfaceof a bush hole.(2) Since the stylus 3 is easily broken, the main spindle needs to beoperated at a low speed in order to prevent the breakage of the stylus3, so that the measurement takes a long time.(3) Every time the measuring head 2 is replaced because of the failureof the stylus 3, or the like, it is necessary to perform calibrationusing a dial gauge, which increases the time taken for the measurement.

On the other hand, an air micrometer has been known as a non-contactsensor, which enables measurement in a short time and at high accuracy.Part (a) of FIG. 22 is a view showing the outline of a conventional airmicrometer, and Part (b) of FIG. 22 is a view showing the outline of acalibration device for the air micrometer.

As shown in Part (a) of FIG. 22, a measuring head 11 of the conventionalair micrometer includes a measuring-head body portion 14 and ameasuring-head tip portion 12 formed on the distal end of themeasuring-head body portion 14. In the measuring-head tip portion 12, afirst measurement air nozzle 16A and a second measurement air nozzle 16Bare formed to extend respectively in the opposite directions to eachother along the radial direction of the measuring-head tip portion 12.In the measuring-head body portion 14, a measurement air supply passage15 communicating with the first measurement air nozzle 16A and thesecond measurement air nozzle 16B is formed.

In the measurement, after the measuring head 11 (the measuring-head tipportion 12) is inserted into a hole 13 a of a measurement target 13 asillustrated, measurement air is supplied from a measurement air supplysource 17, through an A/D converter 18, to the measurement air supplypassage 15 in the measuring-head body portion 14. After passing throughthe measurement air supply passage 15, the measurement air is dividedinto two flows, which are thus jetted from the first measurement airnozzle 16A and the second measurement air nozzle 16B, respectively. Inthis event, the A/D converter 18 detects the pressure of the measurementair (which corresponds to the flow rate of the measurement air),converts the detection signal into a digital signal, and outputs thedigital signal to a control device (illustration of which is omitted).The control device obtains the flow rate of the measurement air from thepressure detection signal outputted from the A/D converter 18, andobtains the diameter D1 of the measurement target hole 13 a on the basisof data on the flow rate of the measurement air and pre-stored datarepresenting the relationship between the hole diameter and the flowrate of the measurement air.

In addition, the data representing the relationship between themeasurement flow rate and the hole diameter is obtained in advance byuse of an air-micrometer calibration device (a master gauge) 19 as shownin Part (b) of FIG. 22. Specifically, after the measuring head 11 (themeasuring-head tip portion 12) is inserted into a master hole 19 a,having a predetermined diameter D2, of the air-micrometer calibrationdevice 19 as illustrated, the measurement air is supplied from the airsupply source 17, through the A/D converter 18, to the air supplypassage 15 in the measurement-head main body 14. After passing throughthe measurement air supply passage 15, the measurement air is dividedinto two flows, which are thus jetted from the first measurement airnozzle 16A and the second measurement air nozzle 16B, respectively. TheA/D converter detects the pressure of the measurement air (whichcorresponds to the flow rate of the measurement air) in this event,converts the detection signal into a digital signal, and outputs thedigital signal to the control device (not illustrated). The controldevice obtains the flow rate of the measurement air from the pressuredetection signal outputted from the A/D converter 18. This measurementis performed on two types of master holes having different diameters D2,that is, large and small master holes 19 a. Then, the control devicestores data on the flow rate of measurement air and data on the diameterD2 inputted in advance as the aforementioned data representing therelationship between the flow rate of the measurement air and the holediameter.

Patent Document 1: Japanese Patent Application Publication No.2006-284376

Patent Document 2: Japanese Patent Application Publication No. Sho58-114835Patent Document 3: Japanese Patent Application Publication No. Hei6-186009Patent Document 4: Japanese Patent Application Publication No. Hei7-134018

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, the above-described conventional measuring head 11 for the airmicrometer is only capable of detecting the hole diameter D1, butincapable of detecting gaps ΔG1 and ΔG2 each between the outerperipheral surface 12 a of the measuring head 12 and the innerperipheral surface 13 b of the measurement target hole 13 a as shown inPart (a) of FIG. 22. For this reason, even when the measuring head 11 isemployed as it is for the measurement of a bush hole, only the innerdiameter of the bush hole can be measured, but the gaps between theouter peripheral surface 12 a of the measuring-head tip portion 12 andthe inner peripheral surface of the bush hole cannot be measured. Inshort, the amount of eccentricity between the main spindle and the bushhole cannot be measured.

In view of the above-described circumstances, an object of the presentinvention is to provide a measuring head for an air micrometer which iscapable of measuring the amount of eccentricity between a main spindleand a bush hole.

Means for Solving the Problems

A measuring head for an air micrometer of a first invention for solvingthe above-described problems is a measuring head for an air micrometer,the measuring head configured to be mounted on a main spindle of amachine tool at the time of measurement and inserted into a bush hole ofa bush attached to a work table of the machine tool, for measuring anamount of eccentricity between the bush hole and the main spindle,

the measuring head characterized by comprising:

a measuring-head body portion; and

a measuring-head tip portion provided on a distal end of themeasuring-head body portion, and configured to be inserted into the bushhole at the time of the measurement,

the measuring head characterized in that

one or a plurality of measurement air nozzles are formed in themeasuring-head tip portion, the measurement air nozzles configured toblow measurement air to a gap between an outer peripheral surface of themeasuring-head tip portion and an inner peripheral surface of the bushhole respectively through jetting openings in the outer peripheralsurface at the time of measurement,

individual measurement air supply passages corresponding to therespective measurement air nozzles are formed in the measurement-headbody portion, and

the measurement air is supplied to the measurement air nozzlesrespectively through the individual measurement air supply passages.

In addition, a measuring head for an air micrometer of a secondinvention, according to the measuring head for an air micrometer of thefirst invention, is characterized in that

the measurement air nozzles are a first measurement air nozzle and asecond measurement air nozzle each of which is formed to extend in aradial direction of the measuring-head tip portion, and which have anangle of 180 degrees with respect to each other in a circumferentialdirection of the measuring-head tip portion, and

the measurement air supply passages are a first measurement air supplypassage for supplying the measurement air to the first measurement airnozzle and a second measurement air supply passage for supplying themeasurement air to the second measurement air nozzle.

Additionally, a measuring head for an air micrometer of a thirdinvention, according to the measuring head for an air micrometer of thefirst invention, is characterized in that

the measurement air nozzles are a first measurement air nozzle, a secondmeasurement air nozzle, a third measurement air nozzle, and a fourthmeasurement air nozzle each of which is formed to extend in a radialdirection of the measuring-head tip portion, and each of which has anangle of 90 degrees with respect to its adjacent ones in acircumferential direction of the measuring-head tip portion, and

the measurement air supply passages are a first measurement air supplypassage for supplying the measurement air to the first measurement airnozzle, a second measurement air supply passage for supplying themeasurement air to the second measurement air nozzle, a thirdmeasurement air supply passage for supplying the measurement air to thethird measurement air nozzle and a fourth measurement air supply passagefor supplying the measurement air to the fourth measurement air nozzle.

Moreover, a measuring head for an air micrometer of a fourth invention,according to the measuring head for an air micrometer of the firstinvention, is characterized in that

the measurement air nozzles are a first measurement air nozzle and asecond measurement air nozzle each of which is formed to extend in aradial direction of the measuring-head tip portion, and which have anangle of 90 degrees with respect to each other in a circumferentialdirection of the measuring-head tip portion, and

the measurement air supply passages are a first measurement air supplypassage for supplying the measurement air to the first measurement airnozzle and a second measurement air supply passage for supplying themeasurement air to the second measurement air nozzle.

Further, a measuring head for an air micrometer of a fifth invention,according to the measuring head for an air micrometer of the firstinvention, is characterized in that

the measurement air nozzles are a single measurement air nozzle formedto extend in a radial direction of the measuring-head tip portion, and

the measurement air supply passages are a single measurement air supplypassage for supplying the measurement air to the single measurement airnozzle.

Furthermore, a measuring head for an air micrometer of a sixthinvention, according to the measuring head for an air micrometer of thesecond invention, is characterized in that

the measurement air is supplied from a first measurement air supplypassage and a second measurement air supply passage that are formed in asupport portion of the main spindle, through a first measurement airsupply passage and a second measurement air supply passage in a rotaryjoint mounted on the measuring-head body portion, to the firstmeasurement air supply passage and the second measurement air supplypassage in the measuring-head body portion, respectively, or

the measurement air is supplied from a first measurement air supplypassage and a second measurement air supply passage that are formed in asupport portion of the main spindle, through a first measurement airsupply passage and a second measurement air supply passage in a rotaryjoint mounted on the main spindle as well as a first measurement airsupply passage and a second measurement air supply passage that areformed in the main spindle, to the first measurement air supply passageand the second measurement air supply passage in the measuring-head bodyportion, respectively.

Also, a measuring head for an air micrometer of a seventh invention,according to the measuring head for an air micrometer of the fifthinvention, is characterized in that

the measurement air is supplied from a measurement air supply passagethat is formed in a support portion of the main spindle, through ameasurement air supply passage in a rotary joint mounted on themeasuring-head body portion, to the measurement air supply passage inthe measuring head body portion, or

the measurement air is supplied from a measurement air supply passagethat is formed in a support portion of the main spindle, through ameasurement air supply passage in a rotary joint mounted on the mainspindle as well as a measurement air supply passage that is formed inthe main spindle, to the measurement air supply passage in the measuringhead body portion.

In addition, a measuring head for an air micrometer of an eighthinvention, according to the measuring head for an air micrometer of thethird invention, is characterized in that

the measurement air is supplied from a first measurement air supplypassage, a second measurement air supply passage, a third measurementair supply passage, and a fourth measurement air supply passage that areformed in a support portion of the main spindle, to the firstmeasurement air supply passage, the second measurement air supplypassage, the third measurement air supply passage, and the fourthmeasurement air supply passage in the measuring-head body portion,respectively.

Additionally, a measuring head for an air micrometer of a ninthinvention, according to the measuring head for an air micrometer of thethird invention, is characterized in that

the measurement air is supplied from a first measurement air supplypassage and a second measurement air supply passage that are formed in asupport portion of the main spindle, to the first measurement air supplypassage and the second measurement air supply passage in themeasuring-head body portion, respectively.

Moreover, a measuring head for an air micrometer of a tenth invention,according to any one of the measuring heads for an air micrometer of thefirst to ninth inventions, is characterized in that

an air-blow nozzle is formed in the measuring-head tip portion, theair-blow nozzle configured to jet air-blow air toward the innerperipheral surface of the bush hole forward through a jetting opening ina tapered surface on a peripheral edge of a distal end of themeasuring-head tip portion, at the time of measurement and

an air-blow air supply passage for supplying the air-blow air to theair-blow nozzle is formed in the measuring-head body portion.

Further, a measuring head for an air micrometer of an eleventhinvention, according to the measuring head for an air micrometer of thetenth invention, is characterized in that

the air-blow air is supplied from an air-blow air supply passage that isformed in a support portion of the main spindle, to the air-blow airsupply passage in the measuring-head body portion, directly or throughan air-blow air supply passage in a rotary joint mounted on the mainspindle as well as an air-blow air supply passage that is formed in themain spindle.

Furthermore, a measuring head for an air micrometer of a twelfthinvention, according to any one of the measuring heads for an airmicrometer of the first to eleventh inventions, is characterized in that

the measuring-head body portion includes:

a distal-end-side member to which the measuring-head tip portion isfixed;

a proximal-end-side member;

an elastic member interposed between the distal-end-side member and theproximal-end-side member; and

a flexible hose connecting a measurement air supply passage that isformed in the distal-end-side member and a measurement air supplypassage that is formed in the proximal-end-side member to each other.

EFFECTS OF THE INVENTION

According to the measuring head for an air micrometer of the firstinvention, provided is a measuring head for an air micrometer, themeasuring head configured to be mounted on a main spindle of a machinetool at the time of measurement and inserted into a bush hole of a bushattached to a work table of the machine tool, for measuring an amount ofeccentricity between the bush hole and the main spindle, the measuringhead characterized by comprising: a measuring-head body portion; and ameasuring-head tip portion provided on a distal end of themeasuring-head body portion, and configured to be inserted into the bushhole at the time of the measurement, the measuring head characterized inthat one or a plurality of measurement air nozzles are formed in themeasuring-head tip portion, the measurement air nozzles configured toblow measurement air to a gap between an outer peripheral surface of themeasuring-head tip portion and an inner peripheral surface of the bushhole respectively through jetting openings in the outer peripheralsurface at the time of measurement, individual measurement air supplypassages corresponding to the respective measurement air nozzles areformed in the measurement-head body portion, and the measurement air issupplied to the measurement air nozzles respectively through theindividual measurement air supply passages. With this configuration, themeasuring head is capable of measuring, not the inner diameter of thebush hole, but the gap between the outer peripheral surface of themeasuring-head tip portion and the inner peripheral surface of the bushhole. Then, the amount of eccentricity between the main spindle and thebush hole is obtained on the basis of the measured value of the gap, andthe position of the main spindle is controlled in accordance with theamount of eccentricity (that is, the relative position of the mainspindle and the bush hole is corrected), whereby the axis of the mainspindle (the drilling tool) and the axis of the bush hole are caused tocoincide with each other. Therefore, uneven wear of the bush hole can beprevented.

According to the measuring head for an air micrometer of the secondinvention, provided is the measuring head for an air micrometer of thefirst invention, characterized in that the measurement air nozzles are afirst measurement air nozzle and a second measurement air nozzle each ofwhich is formed to extend in a radial direction of the measuring-headtip portion, and which have an angle of 180 degrees with respect to eachother in a circumferential direction of the measuring-head tip portion,and the measurement air supply passages are a first measurement airsupply passage for supplying the measurement air to the firstmeasurement air nozzle and a second measurement air supply passage forsupplying the measurement air to the second measurement air nozzle. Withthis configuration, the measuring head is capable of measuring, not theinner diameter of the bush hole, but the gaps between the outerperipheral surface of the measuring-head tip portion and the innerperipheral surface of the bush hole at both sides in the first radialdirection and at both sides in the second radial direction to each ofwhich the measuring-head tip portion is perpendicular, by rotating themeasuring head by 90 degrees by means of the main spindle. Accordingly,the amounts of eccentricity between the main spindle and the bush holeare obtained on the basis of the measured values of the gaps (forexample, by calculation of equations (1) and (2) described later), andthen, the position of the main spindle is controlled in accordance withthe amounts of eccentricity (that is, the relative position between themain spindle and the bush hole is corrected), whereby the axis of themain spindle (the drilling tool) and the axis of the bush hole arecaused to coincide with each other. Therefore, uneven wear of the bushhole can be prevented.

According to the measuring head for an air micrometer of the thirdinvention, provided is the measuring head for an air micrometer of thefirst invention, characterized in that the measurement air nozzles are afirst measurement air nozzle, a second measurement air nozzle, a thirdmeasurement air nozzle, and a fourth measurement air nozzle each ofwhich is formed to extend in a radial direction of the measuring-headtip portion, and each of which has an angle of 90 degrees with respectto its adjacent ones in a circumferential direction of themeasuring-head tip portion, and the measurement air supply passages area first measurement air supply passage for supplying the measurement airto the first measurement air nozzle, a second measurement air supplypassage for supplying the measurement air to the second measurement airnozzle, a third measurement air supply passage for supplying themeasurement air to the third measurement air nozzle and a fourthmeasurement air supply passage for supplying the measurement air to thefourth measurement air nozzle. With this configuration, the measuringhead is capable of measuring, not the inner diameter of the bush hole,but the gaps between the outer peripheral surface of the measuring-headtip portion and the inner peripheral surface of the bush hole at bothsides in the first radial direction and at both sides in the secondradial direction to each of which the measuring-head tip portion isperpendicular. Accordingly, the amounts of eccentricity between the mainspindle and the bush hole are obtained on the basis of the measuredvalues of the gaps (for example, by calculation of equations (1) and (2)described later), and then, the position of the main spindle iscontrolled in accordance with the amounts of eccentricity (that is, therelative position between the main spindle and the bush hole iscorrected), whereby the axis of the main spindle (the drilling tool) andthe axis of the bush hole are caused to coincide with each other.Therefore, uneven wear of the bush hole can be prevented.

According to the measuring head for an air micrometer of the fourthinvention, provided is the measuring head for an air micrometer of thefirst invention, characterized in that the measurement air nozzles are afirst measurement air nozzle and a second measurement air nozzle each ofwhich is formed to extend in a radial direction of the measuring-headtip portion, and which have an angle of 90 degrees with respect to eachother in a circumferential direction of the measuring-head tip portion,and the measurement air supply passages are a first measurement airsupply passage for supplying the measurement air to the firstmeasurement air nozzle and a second measurement air supply passage forsupplying the measurement air to the second measurement air nozzle. Withthis configuration, the measuring head is capable of measuring, not theinner diameter of the bush hole, but the gaps between the outerperipheral surface of the measuring-head tip portion and the innerperipheral surface of the bush hole in the first radial direction andthe second radial direction to each of which directions themeasuring-head tip portion is perpendicular. Accordingly, the amounts ofeccentricity between the main spindle and the bush hole are obtained onthe basis of the measured values of the gaps (for example, bysubtracting the measured values of the gaps from values of gaps betweenthe outer peripheral surface of the measuring-head tip portion and theinner peripheral surface of the bush hole at the time when there is noeccentricity), and then, the position of the main spindle is controlledin accordance with the amounts of eccentricity (that is, the relativeposition between the main spindle and the bush hole is corrected),whereby the axis of the main spindle (the drilling tool) and the axis ofthe bush hole are caused to coincide with each other. Therefore, unevenwear of the bush hole can be prevented.

According to the measuring head for an air micrometer of the fifthinvention, provided is the measuring head for an air micrometer of thefirst invention, characterized in that the measurement air nozzles are asingle measurement air nozzle formed to extend in a radial direction ofthe measuring-head tip portion, and the measurement air supply passagesare a single measurement air supply passage for supplying themeasurement air to the single measurement air nozzle. With thisconfiguration, the measuring head is capable of measuring, not the innerdiameter of the bush hole, but the gaps between the outer peripheralsurface of the measuring-head tip portion and the inner peripheralsurface of the bush hole in the first radial direction and the secondradial direction to each of which directions the measuring-head tipportion is perpendicular, by rotating the measuring head by 90 degreesby means of the main spindle, for example. Accordingly, the amounts ofeccentricity between the main spindle and the bush hole are obtained onthe basis of the measured values of the gaps (for example, bysubtracting the measured values of the gaps from values of gaps betweenthe outer peripheral surface of the measuring-head tip portion and theinner peripheral surface of the bush hole at the time when there is noeccentricity), and then, the position of the main spindle is controlledin accordance with the amounts of eccentricity (that is, the relativeposition between the main spindle and the bush hole is corrected),whereby the axis of the main spindle (the drilling tool) and the axis ofthe bush hole are caused to coincide with each other. Therefore, unevenwear of the bush hole can be prevented.

According to the measuring head for an air micrometer of the sixthinvention, provided is the measuring head for an air micrometer of thesecond invention, characterized in that the measurement air is suppliedfrom a first measurement air supply passage and a second measurement airsupply passage that are formed in a support portion of the main spindle,through a first measurement air supply passage and a second measurementair supply passage in a rotary joint mounted on the measuring-head bodyportion, to the first measurement air supply passage and the secondmeasurement air supply passage in the measuring-head body portion,respectively, or the measurement air is supplied from a firstmeasurement air supply passage and a second measurement air supplypassage that are formed in a support portion of the main spindle,through a first measurement air supply passage and a second measurementair supply passage in a rotary joint mounted on the main spindle as wellas a first measurement air supply passage and a second measurement airsupply passage that are formed in the main spindle, to the firstmeasurement air supply passage and the second measurement air supplypassage in the measuring-head body portion, respectively. With thisconfiguration, the following effect and the like can be obtained. Themeasurement air can be supplied from the support portion of the mainspindle, and there is no need to connect such supply means as a hose forsupplying measurement air, directly to the measuring head. Therefore,operations for measurement, such as attachment and detachment of themeasuring head to and from the main spindle, are facilitated.

According to the measuring head for an air micrometer of the seventhinvention, provided is the measuring head for an air micrometer of thefifth invention, characterized in that the measurement air is suppliedfrom a measurement air supply passage that is formed in a supportportion of the main spindle, through a measurement air supply passage ina rotary joint mounted on the measuring-head body portion, to themeasurement air supply passage in the measuring head body portion, orthe measurement air is supplied from a measurement air supply passagethat is formed in a support portion of the main spindle, through ameasurement air supply passage in a rotary joint mounted on the mainspindle as well as a measurement air supply passage that is formed inthe main spindle, to the measurement air supply passage in the measuringhead body portion. With this configuration, the following effect and thelike can be obtained. The measurement air can be supplied from thesupport portion of the main spindle, and there is no need to connectsuch supply means as a hose for supplying measurement air, directly tothe measuring head. Therefore, operations for measurement, such asattachment and detachment of the measuring head to and from the mainspindle, are facilitated.

According to the measuring head for an air micrometer of the eighthinvention, provided is the measuring head for an air micrometer of thethird invention, characterized in that the measurement air is suppliedfrom a first measurement air supply passage, a second measurement airsupply passage, a third measurement air supply passage, and a fourthmeasurement air supply passage that are formed in a support portion ofthe main spindle, to the first measurement air supply passage, thesecond measurement air supply passage, the third measurement air supplypassage, and the fourth measurement air supply passage in themeasuring-head body portion, respectively. With this configuration, thefollowing effect and the like can be obtained. The measurement air canbe supplied from the support portion of the main spindle, and there isno need to connect such supply means as a hose for supplying measurementair, directly to the measuring head. Therefore, operations formeasurement, such as attachment and detachment of the measuring head toand from the main spindle, are facilitated.

According to the measuring head for an air micrometer of the ninthinvention, provided is the measuring head for an air micrometer of thefourth invention, characterized in that the measurement air is suppliedfrom a first measurement air supply passage and a second measurement airsupply passage that are formed in a support portion of the main spindle,to the first measurement air supply passage and the second measurementair supply passage in the measuring-head body portion, respectively.With this configuration, the following effect and the like can beobtained. The measurement air can be supplied from the support portionof the main spindle, and there is no need to connect such supply meansas a hose for supplying measurement air, directly to the measuring head.Therefore, operations for measurement, such as attachment and detachmentof the measuring head to and from the main spindle, are facilitated.

According to the measuring head for an air micrometer of the tenthinvention, provided is any one of the measuring heads for an airmicrometer of the first to ninth inventions, characterized in that anair-blow nozzle is formed in the measuring-head tip portion, theair-blow nozzle configured to jet air-blow air toward the innerperipheral surface of the bush hole forward through a jetting opening ina tapered surface on a peripheral edge of a distal end of themeasuring-head tip portion, at the time of measurement and an air-blowair supply passage for supplying the air-blow air to the air-blow nozzleis formed in the measuring-head body portion. With this configuration,even if foreign matter, such as a chip, is attached onto the innerperipheral surface of the bush hole, it is possible to perform the gapmeasurement after removing the foreign matter from the inner peripheralsurface of the bush hole with the air blow, so that highly-precise gapmeasurement can be performed.

According to the measuring head for an air micrometer of the eleventhinvention, provided is the measuring head for an air micrometer of thetenth invention, characterized in that the air-blow air is supplied froman air-blow air supply passage that is formed in a support portion ofthe main spindle, to the air-blow air supply passage in themeasuring-head body portion, directly or through an air-blow air supplypassage in a rotary joint mounted on the main spindle as well as anair-blow air supply passage that is formed in the main spindle. Withthis configuration, the following effect and the like can be obtained.The air-blow air can be supplied from the support portion of the mainspindle, and there is no need to connect such supply means as a hose forsupplying air-blow air, directly to the measuring head. Therefore,operations for measurement, such as attachment and detachment of themeasuring head to and from the main spindle, are facilitated.

According to the measuring head for an air micrometer of the twelfthinvention, provided is any one of the measuring heads for an airmicrometer of the first to eleventh inventions, characterized in thatthe measuring-head body portion includes: a distal-end-side member towhich the measuring-head tip portion is fixed; a proximal-end-sidemember; an elastic member interposed between the distal-end-side memberand the proximal-end-side member; and a flexible hose connecting ameasurement air supply passage that is formed in the distal-end-sidemember and a measurement air supply passage that is formed in theproximal-end-side member to each other. With this configuration, even ifthe measuring-head tip portion comes into contact with the bush duringthe insertion of the measuring-head tip portion into the bush hole, theelastic member is expanded or compressed to cause the measuring-head tipportion to move toward the proximal end, so that the impact at the timeof the contact is mitigated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Part (a) of FIG. 1 is a view showing an example of a machine toolfor which a measuring head for an air micrometer according to Embodiment1 of the present invention is employed, and Part (b) of FIG. 1 is amain-part enlarged view showing a state where the measuring head ismounted on a main spindle of the machine tool.

FIG. 2 is a partially cut-away side view showing the measuring head.

FIG. 3 Part (a) of FIG. 3 is a cross-sectional view showing a part ofthe measuring head, Part (b) of FIG. 3 is a view in the direction of thearrow A in FIG. 2, Part (c) of FIG. 3 is a cross-sectional view takenalong the line B-B in FIG. 2 and viewed in the direction of the arrowsB, and Part (d) of FIG. 3 is a cross-sectional view taken along the lineC-C in FIG. 2 and viewed in the direction of the arrows C.

FIG. 4 is a system configurational diagram of the air micrometer.

FIG. 5 Part (a) of FIG. 5 is a view in the direction of the arrow D inFIG. 4, and Part (b) of FIG. 5 is a view showing a state where themeasuring head is rotated by 90 degrees from the state shown in Part (a)of FIG. 5.

FIG. 6 is a graph for explaining data representing the relationshipbetween the flow rate of a measurement air and a gap.

FIG. 7 Part (a) of FIG. 7 is a cross-sectional view of an air-micrometercalibration device (a master gauge) used for calibration of themeasuring head, Part (b) of FIG. 7 is a view in the direction of thearrow E in Part (a) of FIG. 7, and Part (c) of FIG. 7 is across-sectional view taken along the line F-F in Part (a) of FIG. 7 andviewed in the direction of the arrows F.

FIG. 8 Part (a) of FIG. 8 is a view showing how the measuring head iscalibrated using the air-micrometer calibration device, and Part (b) ofFIG. 8 is a view in the direction of the arrow G in Part (a) of FIG. 8.

FIG. 9 is a side view of a measuring head for an air micrometeraccording to Embodiment 2 of the present invention.

FIG. 10 Part (a) of FIG. 10 is a cross-sectional view showing part ofthe measuring head, Part (b) of FIG. 10 is a view in the direction ofthe arrow H in FIG. 9, Part (c) of FIG. 10 is a cross-sectional viewtaken along the line I-I in FIG. 9 and viewed in the direction of thearrows I, Part (d) of FIG. 10 is a cross-sectional view taken along theline J-J in FIG. 9 and viewed in the direction of the arrows J, Part (e)of FIG. 10 is a cross-sectional view taken along the line K-K in FIG. 9and viewed in the direction of the arrows K, and Part (f) of FIG. 10 isa cross-sectional view taken along the line L-L in FIG. 9 and viewed inthe direction of the arrows L.

FIG. 11 is a system configurational diagram of the air micrometer.

FIG. 12 is a view in the direction of the arrow M in FIG. 11.

FIG. 13 is a view showing how the measuring head is calibrated using anair-micrometer calibration device (similar to Part (b) of FIG. 8).

FIG. 14 Part (a) of FIG. 14 is a side view of a main part of a measuringhead for an air micrometer according to Embodiment 3 of the presentinvention, Part (b) of FIG. 14 is a view in the direction of the arrow Nin Part (a) of FIG. 14, Part (c) of FIG. 14 is a cross-sectional viewtaken along the line O-O in Part (a) of FIG. 14 and viewed in thedirection of the arrows O, Part (d) of FIG. 14 is a cross-sectional viewtaken along the line P-P in Part (a) of FIG. 14 and viewed in thedirection of the arrows P, and Part (e) of FIG. 14 is a cross-sectionalview taken along the line Q-Q in Part (a) of FIG. 14 and viewed in thedirection of the arrows Q.

FIG. 15 is a view showing how gap measurement is performed by themeasuring head (similar to FIG. 5).

FIG. 16 is a view showing how the measuring head is calibrated using anair-micrometer calibration device (similar to Part (b) of FIG. 8).

FIG. 17 shows a method of calculating an amount of eccentricity. Part(a) of FIG. 17 is a view showing a state where a measuring-head tipportion and a bush hole are not eccentric from each other, Part (b) ofFIG. 17 is a view showing a state where the measuring-head tip portionis eccentric from the bush hole only in the X-axis direction, and Part(c) of FIG. 17 is a main-part enlarged view of the state shown in Part(b) of FIG. 17.

FIG. 18 Part (a) of FIG. 18 is a side view of a main part of a measuringhead for an air micrometer according to Embodiment 4 of the presentinvention, Part (b) of FIG. 18 is a view in the direction of the arrow Rin Part (a) of FIG. 18, Part (c) of FIG. 18 is a cross-sectional viewtaken along the line S-S in Part (a) of FIG. 18 and viewed in thedirection of the arrows S, and Part (d) of FIG. 18 is a cross-sectionalview taken along the line V-V in Part (a) of FIG. 18 and viewed in thedirection of the arrow V.

FIG. 19 Part (a) of FIG. 19 is a view showing how gap measurement isperformed by the measuring head (similar to FIG. 5), and Part (h) ofFIG. 19 is a view showing a state where the measuring head is rotated by90 degrees from the state shown in Part (a) of FIG. 19 (similar to FIG.5).

FIG. 20 is a view showing how the measuring head is calibrated using theair-micrometer calibration device (similar to Part (b) of FIG. 8).

FIG. 21 Part (a) of FIG. 21 is a side view of a touch sensor, and Part(b) of FIG. 21 is a view in the direction of the arrow W in Part (a) ofFIG. 21.

FIG. 22 Part (a) of FIG. 22 is a view showing the outline of aconventional air micrometer, and Part (b) of FIG. 22 is a view showingthe outline of a calibration device for the air micrometer.

EXPLANATION OF REFERENCE NUMERALS

-   21 MACHINE TOOL; 22 BED; 23 WORK TABLE; 24 COLUMN; 25 MAIN-SPINDLE    HEAD; 26 MAIN SPINDLE; 27 BUSH ATTACHMENT JIG; 27 a HORIZONTAL    PORTION; 27 b VERTICAL PORTION; 28, 29, 30 RAIL; 31 BUSH; 31 a BUSH    HOLE; 31 b INNER PERIPHERAL SURFACE; 32 DRILLING TOOL; 41 MEASURING    HEAD; 42 MEASURING-HEAD BODY PORTION; 43 MEASURING-HEAD TIP PORTION;    43 a OUTER PERIPHERAL SURFACE; 45 CONNECTION PORTION; 46 CASE; 46 a    INNER PERIPHERAL SURFACE; 47 SCREW; 48 SPIGOT FITTING PORTION; 49,    50 TAPERED SURFACE; 51A FIRST MEASUREMENT AIR NOZZLE (MEASUREMENT    AIR NOZZLE); 51B SECOND MEASUREMENT AIR NOZZLE;-   51C THIRD MEASUREMENT AIR NOZZLE; 51D FOURTH MEASUREMENT AIR NOZZLE;    51A-1, 51B-1, 51C-1, 51D-1 JETTING OPENING; 52A, 52B, 52C, 52D    AIR-BLOW NOZZLE; 52A-1, 52B-1, 52C-1, 52D-1 JETTING OPENING; 53A    FIRST MEASUREMENT AIR SUPPLY PASSAGE, MEASUREMENT AIR SUPPLY    PASSAGE; 53B SECOND MEASUREMENT AIR SUPPLY PASSAGE; 53 r THIRD    MEASUREMENT AIR SUPPLY PASSAGE; 53D FOURTH MEASUREMENT AIR SUPPLY    PASSAGE; 54 PROXIMAL-END-SIDE MEMBER; 55A FIRST MEASUREMENT AIR    SUPPLY PASSAGE, MEASUREMENT AIR SUPPLY PASSAGE; 55B SECOND    MEASUREMENT AIR SUPPLY PASSAGE; 55C THIRD MEASUREMENT AIR SUPPLY    PASSAGE; 55D FOURTH MEASUREMENT AIR SUPPLY PASSAGE; 56 AIR-BLOW AIR    SUPPLY PASSAGE; 58 LONG HOLE; 59 PROXIMAL END PORTION; 60 SHAFT    PORTION; 61 DISTAL END PORTION; 62 PROXIMAL SIDE END WALL; 62A HOLE;    63A FIRST MEASUREMENT AIR SUPPLY PASSAGE; 63B SECOND MEASUREMENT AIR    SUPPLY PASSAGE; 63C THIRD MEASUREMENT AIR SUPPLY PASSAGE; 63D FOURTH    MEASUREMENT AIR SUPPLY PASSAGE; 64A, 64B, 64C, 64D HOSE; 65 AIR-BLOW    AIR SUPPLY PASSAGE;-   66 SPACE PORTION; 67 ROTARY JOINT; 68A FIRST MEASUREMENT AIR SUPPLY    PASSAGE; 68B SECOND MEASUREMENT AIR SUPPLY PASSAGE; 69A FIRST    COUPLER; 69B SECOND COUPLER; 69C THIRD COUPLER; 69D FOURTH COUPLER;    70A FIRST MEASUREMENT AIR SUPPLY PASSAGE; 70B SECOND MEASUREMENT AIR    SUPPLY PASSAGE; 71 ROTARY JOINT; 72 AIR-BLOW AIR SUPPLY PASSAGE; 73    AIR-BLOW AIR SUPPLY PASSAGE, 74 COIL SPRING; 75 AIR-BLOW AIR SUPPLY    PASSAGE; 76A FIRST MEASUREMENT AIR SUPPLY SOURCE; 76B SECOND    MEASUREMENT AIR SUPPLY SOURCE; 76C THIRD MEASUREMENT AIR SUPPLY    SOURCE; 76D FOURTH MEASUREMENT AIR SUPPLY SOURCE; 77A FIRST A/D    CONVERTER; 77B SECOND A/D CONVERTER; 77C THIRD A/D CONVERTER; 77D    FOURTH A/D CONVERTER; 78 NC SYSTEM; 79 AIR-BLOW AIR SUPPLY SOURCE;    80 SEQUENCER; 81 CONTROL DEVICE; 91 AIR-MICROMETER CALIBRATION    DEVICE; 92 HOUSING HOLE; 93 CLAMPING SLEEVE; 93 a INNER PERIPHERAL    SURFACE; 94 MEASURING-HEAD INSERTION HOLE; 95 SMALL-DIAMETER MASTER    HOLE; 95 a INNER PERIPHERAL SURFACE; 96 LARGE-DIAMETER MASTER HOLE;    96 a INNER PERIPHERAL SURFACE; 97 HYDRAULIC PRESSURE CHAMBER; 98    PRESSURE OIL SUPPLY PASSAGE; 99 HOSE

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, Embodiments of the present invention will be described indetail on the basis of the drawings.

Embodiment 1

Part (a) of FIG. 1 is a view showing an example of a machine tool forwhich a measuring head for an air micrometer according to Embodiment 1of the present invention is employed, and Part (b) of FIG. 1 is amain-part enlarged view showing a state where the measuring head ismounted on a main spindle of the machine tool. FIG. 2 is a partiallycut-away side view showing the measuring head. Part (a) of FIG. 3 is across-sectional view showing a part of the measuring head, Part (b) ofFIG. 3 is a view in the direction of the arrow A in FIG. 2, Part (c) ofFIG. 3 is a cross-sectional view taken along the line B-B in FIG. 2 andviewed in the direction of the arrows B, and Part (d) of FIG. 3 is across-sectional view taken along the line C-C in FIG. 2 and viewed inthe direction of the arrows C. FIG. 4 is a system configurationaldiagram of the air micrometer. Part (a) of FIG. 5 is a view in thedirection of the arrow D in FIG. 4, and Part (b) of FIG. 5 is a viewshowing a state where the measuring head is rotated by 90 degrees fromthe state shown in Part (a) of FIG. 5. FIG. 6 is a graph for explainingdata representing the relationship between the flow rate of ameasurement air and a gap.

Moreover, Part (a) of FIG. 7 is a cross-sectional view of anair-micrometer calibration device (a master gauge) used for calibrationof the measuring head, Part (b) of FIG. 7 is a view in the direction ofthe arrow E in Part (a) of FIG. 7, and Part (c) of FIG. 7 is across-sectional view taken along the line F-F in Part (a) of FIG. 7 andviewed in the direction of the arrows F. Part (a) of FIG. 8 is a viewshowing how the measuring head is calibrated using the air-micrometercalibration device, and Part (b) of FIG. 8 is a view in the direction ofthe arrow G in Part (a) of FIG. 8.

A machine tool 21 illustrated in Part (a) of FIG. 1 includes a bed 22, awork table 23 provided on the bed 22, a column 24, a main-spindle head25, a main spindle 26, a bush attachment jig 27, and the like.

The column 24 is capable of moving along rails 28 provided on an uppersurface of the bed 22 in a direction (the X-axis direction)perpendicular to the plane of Part (a) of FIG. 1. The work table 23 iscapable of moving along rails 29 provided on the upper surface of thebed 22 in a left-right direction (the Z-axis direction) in Part (a) ofFIG. 1. The main-spindle head 25, which is a support portion of the mainspindle 26, is capable of moving along rails 30 provided on a frontsurface of the column 24 in an up-down direction (the Y-axis direction).The illustrated machine tool is a horizontal type. So, the main spindle26 is provided in the main-spindle head 25 with the axial direction ofthe main spindle 26 made horizontal, and is rotatably supported by themain-spindle head 25. The column 24, the work table 23, and themain-spindle head 26 are driven by unillustrated drive mechanisms forthe respective axes, such as a feed screw mechanism, thereby movinglinearly in the X-axis direction, the Z-axis direction, and the Y-axisdirection, respectively. The main spindle 26 is rotationally driven byan unillustrated main-spindle motor.

The bush attachment jig 27 has a horizontal portion 27 a and a verticalportion 27 b, and is fixed onto the work table 23. A workpiece W, suchas a cylinder block or a valve body of an engine, is placed on thehorizontal portion 27 a of the bush attachment jig 27, and is fixedthereto by fixing means such as hydraulic pressure. A bush 31 isattached to the vertical portion of the bush attachment jig 27. The bush31 is a cylindrical member that has a bush hole 31 a having a circularcross section in a center portion of the bush 31. On the other hand, along drilling tool 32 is mounted on the main spindle 26. The drillingtool 32 is rotationally driven with the main spindle 26 while thedrilling tool 32 is inserted through the bush hole 31 a so that thevibration thereof is suppressed by the bush 31. In this way, a drillingprocess is performed to drill a hole 33, such as a crank hole or a spoolhole, which requires a strict coaxiality.

Meanwhile, the amount of eccentricity between the main spindle 26 andthe bush hole 31 a is measured on a regular basis in order to prevent aninner peripheral surface 31 b of the bush hole 31 a from being unevenlyworn because the axis of the main spindle 26 (the drilling tool 32) andthe axis of the bush hole 31 a are misaligned (because the main spindle26 and the bush hole 31 a are caused to be eccentric) due to thermaldeformation of the machine tool 21, or the like.

In this case, a measuring head 41 of the air micrometer is mounted onthe main spindle 26 in place of the drilling tool 32 as shown in Part(b) of FIG. 1, and thereafter, is inserted into the bush hole 31 a.Thereby, gap measurement (measurement of the amount of eccentricitybetween the main spindle 26 and the bush hole 31 a) is performed (whichwill be described later in detail). It should be noted that the gapmeasurement in this case may be performed not only on the bush 31 thatis actually used for the drilling process. A bush 31 that is dedicatedto the gap measurement may be provided to the bush attachment jig 27 orin a vicinity thereof as indicated by an alternate long and short dashline in Part (a) of FIG. 1, and the gap measurement may be performed onthe bush 31 dedicated to the gap measurement.

As shown in FIG. 2 and Part (a) of FIG. 3 to Part (d) of FIG. 3, themeasuring head 41 of the air micrometer of Embodiment 1 has a columnarmeasuring-head body portion 42 and a columnar measuring-head tip portion43 provided on the distal end of the measuring-head body portion 42. Thedistal end of the measuring-head body portion 42 is formed into aconnection portion 45 (a distal-end-side member) integral with themeasuring-head tip portion 43. A spigot fitting portion 48 of theconnection portion 45 is fitted into a case 46 of the measuring-headbody portion 42. In addition, a plurality of long holes (recessedportions) 58 are formed in an outer peripheral surface of the case 46.The connection portion 45 is screwed to the case 46 with screws 47inserted from these long holes 58.

A peripheral edge of the distal end of the measuring-head tip portion 43is formed into a tapered surface 49, while a peripheral edge of theproximal end of the measuring-head tip portion 43 is also formed into atapered surface 50. The tapered surface 49 is inclined inward in theradial direction of the measuring-head tip portion 43 as extending tothe distal end of the measuring-head tip portion 43. The tapered surface50 is inclined inward in the radial direction of the measuring-head tipportion 43 as extending to the proximal end of the measuring-head tipportion 43.

Moreover, two measurement air nozzles 51A and 51B as well as fourair-blow nozzles 52A, 52B, 52C, and 52D are formed in the measuring-headtip portion 43.

The first measurement air nozzle 51A and the second measurement airnozzle 51B are formed to each extend in the radial direction of themeasuring-head tip portion 43, and have an angle of 180 degrees withrespect to each other in the circumferential direction of themeasuring-head tip portion 43. At the time of measurement, the firstmeasurement air nozzle 51A and the second measurement air nozzle 51B jetair toward gaps between an outer peripheral surface 43 a of themeasuring-head tip portion 43 and the inner peripheral surface 31 b ofthe bush hole 31 a through jetting openings 51A-1 and 51B-1 in the outerperipheral surface 43 a. Each of the air-blow nozzles 52A, 52B, 52C, and52D has an angle of 90 degrees with respect to its adjacent ones in thecircumferential direction of the measuring-head tip portion 43. Theair-blow nozzles 52A, 52B, 52C, and 52D jet air-blow air toward theinner peripheral surface 31 b of the bush hole 31 a forward throughjetting openings 52A-1, 52B-1, 52C-1, and 52D-1 in the tapered surface49 on the distal end side. Furthermore, a first measurement air supplypassage 53A connected to the first measurement air nozzle 51A, a secondmeasurement air supply passage 53B connected to the second measurementair nozzle 51B, and an air-blow air supply passage 56 connected to theair-blow nozzles 52A, 52B, 52C, and 52D are formed in the connectionportion 45.

On the other hand, the measuring-head body portion 42 includes the case46, serving as a distal-end-side member, and a proximal-end-side member54, in addition to the aforementioned connection portion 45. The case 46is a cylindrical member, and has a first measurement air supply passage55A and a second measurement air supply passage 55B formed in a thickplate portion thereof. The first measurement air supply passage 55A isconnected to the aforementioned first measurement air supply passage53A. The second measurement air supply passage 55B is connected to theaforementioned second measurement air supply passage 53B.

The proximal-end-side member 54 has a structure in which a distal endportion 61 and a proximal end portion 59 are formed respectively ondistal and proximal sides of a shaft portion 60, the distal end portion61 and the proximal end portion 59 having larger diameters than that ofthe shaft portion 60. The distal end portion 62 is disposed inside thecase 46, and is capable of sliding in the axial direction while being incontact with an inner peripheral surface 46 a of the case 46. The shaftportion 60 is inserted into a hole 62 a of a proximal end side end plate62 of the case 46, and is capable of moving in the axial direction. Inaddition, a coil spring 74 serving as an elastic member is interposedbetween the distal end portion 62 and the connection portion 45 (thespigot portion 48). The coil spring 74 is always pressing forward themeasuring-head tip portion 43 (the connection portion 45). Accordingly,even if the measuring-head tip portion 43 comes into contact with thebush 31 during the insertion of the measuring-head tip portion 43 intothe bush hole 31 a, the coil spring 74 is compressed to cause themeasuring-head tip portion 43 to move together with the case 46 towardthe proximal end as indicated by an alternate long and short dash linein Part (a) of FIG. 3, so that the impact at the time of the contact ismitigated.

A first measurement air supply passage 63A and a second measurement airsupply passage 63B are formed in the proximal-end-side member 54. Afirst hose 64A and a second hose 64B which are flexible are wound aroundan outer peripheral surface of the shaft portion 60. The first hose 64Aconnects the first measurement air supply passage 55A in the case 46 andthe first measurement air supply passage 63A in the proximal-end-sidemember 54 to each other. The second hose 64B connects the secondmeasurement air supply passage 55B in the case 46 and the secondmeasurement air supply passage 63A in the proximal-end-side member 54 toeach other. Accordingly, the first measurement air nozzle 51A issupplied with the measurement air through the first measurement airsupply passage 63A, the first hose 64A, the first measurement air supplypassage 55A, and the first measurement air supply passage 53A, while thesecond measurement air nozzle 51B is supplied with the measurement airthrough the second measurement air supply passage 63B, the second hose64B, the second measurement air supply passage 55B, and the secondmeasurement air supply passage 53B.

On the other hand, an air-blow air supply passage 65 is formed in theproximal-end-side member 54 (the distal end portion 61, the shaftportion 60, and the proximal end portion 59). Accordingly, the air-blownozzles 52A, 52B, 52C, and 52D are supplied with the air-blow airthrough the air-blow air supply passage 65, a space portion 66 betweenthe distal end portion 61 and the connection portion 45 (the spigotportion 48) in the case 46, and the air-blow air supply passage 56.

In addition, a rotary joint 67 is mounted on the outer peripheralsurface of the proximal-end-side member 54. An attachment and detachmentportion 68 is provided on the proximal end of the proximal-end-sidemember 54. The attachment and detachment portion 68 has a structureallowing the measuring head 41 to be attached to and detached from themain spindle 26 as in the case of the drilling tool 32.

A first measurement air supply passage 68A in the rotary joint 67 isconnected through a first coupler 69A to a first measurement air supplypassage 70A formed in the main-spindle head 25. A second measurement airsupply passage 68B in the rotary joint 67 is connected through a secondcoupler 69B to a second measurement air supply passage 70B formed in themain-spindle head 25. Accordingly, the first measurement air supplypassage 63A in the proximal-end-side member 54 is supplied with themeasurement air from the first measurement air supply passage 70A in themain-spindle head 25 through the first measurement air supply passage68A in the rotary joint 67, while the second measurement air supplypassage 63B in the proximal-end-side member 54 is supplied with themeasurement air from the second measurement air supply passage 70B inthe main-spindle head 25 through the second measurement air supplypassage 68B in the rotary joint 67.

In addition, a rotary joint 71 is mounted on the main spindle 26. Anair-blow air supply passage 72 in the rotary joint 71 is connected to anair-blow air supply passage 73 formed in the main-spindle head 25.Accordingly, the air-blow air supply passage 65 in the proximal-end-sidemember 54 is supplied with the air-blow air from the air-blow air supplypassage 73 in the main-spindle head 25 through the air-blow air supplypassage 72 in the rotary joint 71 and an air-blow air supply passage 75formed in the main spindle 26.

Next, the system configuration of the air micrometer and procedures ofoperation of gap measurement will be described on the basis of FIG. 4,Part (a) of FIG. 5 and Part (b) of FIG. 5, as well as FIG. 6. It shouldbe noted that the following operation is performed by controlling theoperations of the drive mechanisms of the respective axes, the rotationof the main-spindle motor, and the like, by use of an NC system(numerical control system) 78.

At the time of gap measurement, first, the measuring head 41 is mountedon the main spindle 26 in place of the drilling tool 32. Then, after themeasuring head 41 is moved to the inlet of the bush hole 31 a, air-blowair is supplied to the air-blow nozzles 52A, 52B, 52C, and 52D in themeasuring-head tip portion 43 (the air-blow air supply passage 73 in themain-spindle head 25) from an air-blow air supply source 79. As aresult, the air-blow air is jetted out from the air-blow nozzles 52A,52B, 52C, and 52D toward the inner peripheral surface 31 b of the bushhole 31 a. Accordingly, if foreign matter, such as a chip, has beenattached on the inner peripheral surface 31 b, the foreign matter isblown out by the air-blow air and is removed from the inner peripheralsurface 31 b.

Thereafter, as shown in FIG. 4, the measuring-head tip portion 43 isinserted into the bush hole 31 a. A measurement instruction is outputtedfrom the NC system 78 to a sequencer 80, and then, ameasurement-direction selection instruction and a measurement startinstruction are outputted from the sequencer 80 to a control device 81of the air micrometer. As a result, the control on A/D converters 77Aand 77B as well as air supply sources 76A and 76B by the control device81 is started, so that the gap measurement in the Y-axis direction andthe gap measurement in the X-axis direction are performed. Any of thesegap measurements in the Y-axis direction and in the X-axis direction maybe performed first. For example, the gap measurement in the Y-axisdirection is performed first as shown in Part (a) of FIG. 5.Subsequently, the measuring head 41 (measurement air 3) is rotated by 90degrees by the control of the NC system 78 on the main spindle 26, andthe gap measurement in the X-axis direction is performed, as shown inPart (b) of FIG. 5.

First, the gap measurement in the Y-axis direction will be described indetail. The measurement air with a pressure adjusted to be constant bypressure adjusting means such as a regulator is supplied, from the firstmeasurement air supply source 76A and the second measurement air supplysource 76B, through the first A/D converter 77A and the second A/Dconverter 77B, to the first measurement air nozzle 51A (the firstmeasurement air supply passage 70A in the main-spindle head 25) and thesecond measurement air nozzle 51B (the second measurement air supplypassage 70B in the main-spindle head 25) in the measuring-head tipportion 43, respectively. As a result, the measurement air is jettedfrom the first measurement air nozzle 51A and the second measurement airnozzle 51B respectively to gaps ΔY1 and ΔY2 each between the outerperipheral surface 43 a of the measuring-head tip portion 43 and theinner peripheral surface 31 b of the bush hole 31 a. In this event, thefirst A/D converter 77A and the second A/D converter 77B detect therespective pressures of the measurement air (which correspond to theflow rates of the measurement air), convert the detection signals intodigital signals, and output the digital signals to the control device81.

The control device 81 obtains the flow rates of the measurement air fromthe pressure detection signals outputted respectively from the first A/Dconverter 77A and the second A/D converter 77B, and then obtains the gapΔY1 and the gap ΔY2 on the basis of the data on the flow rates of themeasurement air and pre-stored data representing the relationshipbetween the flow rate of the measurement air and the gap, as shown inFIG. 6. Further, the control device 81 calculates an amount ofeccentricity ΔY between the main spindle 26 (the drilling tool 32) andthe bush hole 31 a in the Y-axis direction on the basis of the measuredvalues of the gaps ΔY1 and ΔY2 by the following equation (1), andoutputs the amount of eccentricity ΔY to the sequencer 80:

ΔY=(ΔY1−ΔY2)÷2  (1).

Next, the gap measurement in the X-axis direction will be described indetail. As in the case of the gap measurement in the Y-axis direction,the measurement air with a pressure adjusted to be constant by thepressure adjusting means such as a regulator is supplied, from the firstmeasurement air supply source 76A and the second measurement air supplysource 76B, through the first A/D converter 77A and the second A/Dconverter 77B, to the first measurement air nozzle 51A (the firstmeasurement air supply passage 70A in the main-spindle head 25) and thesecond measurement air nozzle 51B (the second measurement air supplypassage 70B in the main-spindle head 25) in the measuring-head tipportion 43, respectively. As a result, the measurement air is jettedfrom the first measurement air nozzle 51A and the second measurement airnozzle 51B respectively to gaps ΔX1 and ΔX2 each between the outerperipheral surface 43 a of the measuring-head tip portion 43 and theinner peripheral surface 31 b of the bush hole 31 a. In this event, thefirst A/D converter 77A and the second A/D converter 77B detect therespective pressures of the measurement air (which correspond to theflow rates of the measurement air), convert the detection signals intodigital signals, and output the digital signals to the control device81.

The control device 81 obtains the flow rates of the measurement air fromthe pressure detection signals outputted respectively from the first A/Dconverter 77A and the second A/D converter 77B, and then obtains the gapΔX1 and the gap ΔX2 on the basis of the data on the flow rates of themeasurement air and pre-stored data representing the relationshipbetween the flow rate of the measurement air and the gap, as shown inFIG. 6. Further, the control device 81 calculates an amount ofeccentricity ΔX between the main spindle 26 (the drilling tool 32) andthe bush hole 31 a in the X-axis direction on the basis of the measuredvalues of the gaps ΔX1 and ΔX2 by the following equation (2), andoutputs the amount of eccentricity ΔX to the sequencer 80:

ΔX=(ΔX1−ΔX2)÷2  (2).

The sequencer 80 stores the amounts of eccentricity ΔX and ΔY receivedfrom the control device 81 into macro variables in the NC system 78.Then, the NC system 78 controls the position of the main spindle 26(that is, corrects the relative position between the main spindle 26 andthe bush hole 31 a) by shifting the X and Y coordinates of the mainspindle 26 in accordance with the amounts of eccentricity ΔX and ΔY. Inthis way, the NC system 78 causes the axis of the main spindle 26 (thedrilling tool 32) and the axis of the bush hole 31 a to coincide witheach other, thereby preventing uneven wear of the bush hole 31 a.

The data representing the relationship between the flow rate of themeasurement air and the gap, as shown in FIG. 6, is obtained bycalibrating the air micrometer using an air-micrometer calibrationdevice (a master gauge) 91 as shown in Part (a) of FIG. 7 to Part (c) ofFIG. 7.

As shown in Part (a) of FIG. 7 to Part (c) of FIG. 7, the air-micrometercalibration device 91 is housed in a housing hole 92. The place wherethe air-micrometer calibration device 91 is housed (the place where thehousing hole 92 is provided) is set as desired, and may be set, forexample, in the bush attachment jig 27 or a vicinity thereof,alternatively, in a tool housing portion or a vicinity thereof.

The air-micrometer calibration device 91 includes a clamping sleeve 93provided in a middle of a measuring-head insertion hole 94, asmall-diameter master hole (small size) 95, and a large-diameter masterhole (large size) 96. The small-diameter master hole 95 has a diameterD1, while the large-diameter master hole 96 has a diameter D2 largerthan D1. The clamping sleeve 93, the small-diameter master hole 95, andthe large-diameter master hole 96 are arranged in series, and also, theaxis of the clamping sleeve 93, the axis of the small-diameter masterhole 95, and the axis of the large-diameter master hole 96 coincide withone another. The clamping sleeve 93 is a sleeve formed of a metalmaterial or the like in a cylindrical shape.

In addition, a cylindrical hydraulic pressure chamber 97, whichsurrounds the periphery of the clamping sleeve 93, and a pressure oilsupply passage 98, which is connected to the hydraulic pressure chamber97, are formed in the air-micrometer calibration device 91. The pressureoil supply passage 98, the hydraulic pressure chamber 97, and theclamping sleeve 93 constitute positioning means. A flexible hose 99 isconnected to the pressure oil supply passage 98. The air-micrometercalibration device 91 is in the floating state. Specifically, nothinginhibiting the air-micrometer calibration device 91 from moving in theradial direction of the master holes 95 and (the direction of the arrowT) is provided around the air-micrometer calibration device 91;accordingly, the air-micrometer calibration device 91 is capable offreely moving in the radial direction (the direction of the arrow T) inthe housing hole 92.

Next, the procedures of calibration operation will be described on thebasis of FIG. 4, Part (a) of FIG. 8 and Part (b) of FIG. 8. It should benoted that the following operation is performed by controlling the drivemechanisms of the respective axes, and the like, by use of the NC system(numerical control system) 78.

In the calibration, first, the measuring head 41 is moved to the inletof the air-micrometer calibration device 91 (the measuring-headinsertion hole 94). Then, air-blow air is supplied from the air-blow airsupply source 79 to the air-blow nozzles 52A, 52B, 52C, and 52D in themeasuring-head tip portion 43 (the air-blow air supply passage 73 in themain-spindle head 25). As a result, the air-blow air is jetted outtoward an inner peripheral surface 93 a of the clamping sleeve 93, aninner peripheral surface 95 a of the small-diameter master hole 95, andan inner peripheral surface 96 a of the large-diameter master hole 96.Accordingly, if foreign matter, such as a chip, has been attached tothese inner peripheral surfaces 93 a, 95 a, and 96 a, the foreign matteris blown out by the air-blow air and is removed from these innerperipheral surfaces 93 a, 95 a, and 96 a. It should be noted that, ifthere is no possibility that foreign matter is attached to the innerperipheral surfaces 93 a, 95 a, and 96 a because of the housing state ofthe air-micrometer calibration device 91, or the like, the air blow doesnot need to be performed.

At the start of the calibration, the measuring-head tip portion 43 isfirst inserted into the small-diameter master hole as shown in Part (a)of FIG. 8. At this time, the measuring-head body portion 42 (the case46) is located inside the clamping sleeve 93. Then, when oil is suppliedfrom an unillustrated pressure oil supply source to the hydraulicpressure chamber 97 through the hose 99 and the pressure oil supplypassage 98, the hydraulic pressure in the hydraulic pressure chamber 97acts on the entire clamping sleeve 93 as indicated by the arrow U,causing the diameter of the clamping sleeve 93 to be slightly reduced,so that the clamping sleeve 93 clamps the measuring-head body portion 42(the case 46). As a result, the axis of the measuring-head tip portion43 and the axis of the small-diameter master hole 95 are caused tocoincide with each other. To put it differently, a gap ΔG1 between theouter peripheral surface 43 a of the measuring-head tip portion 43 andthe inner peripheral surface 95 a of the small-diameter master hole 95is made uniform (a predetermined value) entirely in the circumferentialdirection of the measuring-head tip portion 43 as shown in Part (b) ofFIG. 8.

In this state, as in the case of the gap measurement, the measurementair with a pressure adjusted to be constant by the pressure adjustingmeans such as a regulator is supplied, from the first measurement airsupply source 76A and the second measurement air supply source 76B,through the first A/D converter 77A and the second A/D converter 77B, tothe first measurement air nozzle 51A (the first measurement air supplypassage 70A in the main-spindle head 25) and the second measurement airnozzle 51B (the second measurement air supply passage 70B in themain-spindle head 25) in the measuring-head tip portion 43,respectively. As a result, these flows of the measurement air are jettedrespectively from the first measurement air nozzle 51A and the secondmeasurement air nozzle 51B to the gap ΔG1 between the outer peripheralsurface 43 a of the measuring-head tip portion 43 and the innerperipheral surface 95 a of the small-diameter master hole 95. In thisevent, the first A/D converter 77A and the second A/D converter 77Bdetect the respective pressures of the measurement air (which correspondto the flow rates of the measurement air), convert the detection signalsinto digital signals, and output the digital signals to the controldevice 81, respectively.

Then, the control device 81 obtains the flow rate Q1 of the measurementair from the pressure detection signals outputted respectively from thefirst A/D converter 77A and the second A/D converter 77B, and storesdata on the flow rate Q1 of the measurement air and pre-stored data onthe gap ΔG1 as data of a point P1 representing the relationship betweenthe flow rate Q1 of the measurement air and the gap ΔG1, as shown inFIG. 6.

Next, the pressure oil is discharged from the hydraulic pressure chamber97 through the pressure oil supply passage 98 and the hose 99, so thatthe clamping of the measuring-head body portion 42 (the case 46) by theclamping sleeve 93 is once released. After that, the measuring-head tipportion 43 is inserted into the large-diameter master hole 96. Also inthis case, the measuring-head body portion 42 (the case 46) is locatedinside the clamping sleeve 93. Then, in the same manner as describedabove, oil is supplied from the pressure oil supply source to thehydraulic pressure chamber 97 through the hose 99 and the pressure oilsupply passage 98, so that the clamping sleeve 93 clamps themeasuring-head body portion 42 (the case 46) with the hydraulic pressurein the hydraulic pressure chamber 97. As a result, the axis of themeasuring-head tip portion 43 and the axis of the large-diameter masterhole 96 are caused to coincide with each other. To put it differently, agap ΔG2 between the outer peripheral surface 43 a of the measuring-headtip portion 43 and the inner peripheral surface 96 a of thelarge-diameter master hole 96 is made uniform (a predetermined value)entirely in the circumferential direction of the measuring-head tipportion 43 as shown in Part (b) of FIG. 8.

In this state, as in the case of the small-diameter master hole 95, themeasurement air with a pressure adjusted to be constant by the pressureadjusting means such as a regulator is supplied, from the firstmeasurement air supply source 76A and the second measurement air supplysource 76B, through the first A/D converter 77A and the second A/Dconverter 77B, to the first measurement air nozzle 51A (the firstmeasurement air supply passage 70A in the main-spindle head 25) and thesecond measurement air nozzle 51B (the second measurement air supplypassage 70B in the main-spindle head 25) in the measuring-head tipportion 43, respectively. As a result, the measurement air is jettedfrom the first measurement air nozzle 51A and the second measurement airnozzle 51B to the gap ΔG2 between the outer peripheral surface 43 a ofthe measuring-head tip portion 43 and the inner peripheral surface 96 aof the large-diameter master hole 96. In this event, the first A/Dconverter 77A and the second A/D converter 77B detect the respectivepressures of the measurement air (which correspond to the flow rates ofthe measurement air), convert the detection signals into digitalsignals, and output the digital signals to the control device 81.

Then, the control device 81 obtains the flow rate Q2 of the measurementair from the pressure detection signals outputted respectively from thefirst A/D converter 77A and the second A/D converter 77B, and storesdata on the flow rate Q2 of the measurement air and pre-stored data onthe gap ΔG2 as data of a point P2 representing the relationship betweenthe flow rate Q2 of the measurement air and the gap ΔG2, as shown inFIG. 6. Moreover, data between the point P2 and the aforementioned P1 isobtained by linear interpolation.

Consequently, the data representing the relationship between the flowrate of the measurement air and the gap as shown by a solid line in FIG.6 is obtained. Note that the change in the flow rate of the measurementair is not proportional to the change in the gap, in a range where thegap is very small and in a range where the gap is large as compared tothe area of the flow passage in the measuring head, as indicated by thedash line in FIG. 6. For this reason, the measurement range for the airmicrometer needs to be a range where the change in the flow rate of themeasurement air is proportional to the change in the gap as indicated bythe solid line in FIG. 6.

As described above, according to the measuring head 41 of Embodiment 1,provided is a measuring head 41 for an air micrometer configured to bemounted on the main spindle 26 of the machine tool 21 at the time ofmeasurement and inserted into the bush hole 31 a of the bush 31 attachedto the work table 23 of the machine tool 21, for measuring the amount ofeccentricity between the bush hole 31 a and the main spindle 26. Themeasuring head 41 for an air micrometer is characterized as follows.Specifically, the measuring head 41 includes: the measuring-head bodyportion 42; and the measuring-head tip portion 43 provided on the distalend of the measuring-head body portion 42 and configured to be insertedinto the bush hole 31 a at the time of the measurement. In addition, thefirst measurement air nozzle 51A and the second measurement air nozzle51B are formed to extend in the radial direction of the measuring-headtip portion 43 and have an angle of 180 degrees with respect to eachother in the circumferential direction of the measuring-head tip portion43. The first measurement air nozzle 51A and the second measurement airnozzle 51B are configured to blow measurement air to the gap between theouter peripheral surface 43 a of the measuring-head tip portion 43 andthe inner peripheral surface 31 b of the bush hole 31 a respectivelythrough the jetting openings 51A-1 and 51B-1 in the outer peripheralsurface 43 a at the time of measurement. Moreover, the individualmeasurement air supply passages corresponding to the respectivemeasurement air nozzles 51A and 51B (that is, the supply passageconstituted of the first measurement air supply passages 53A, 55A, and63A as well as the hose 64A, and the supply passage constituted of thefirst measurement air supply passages 53B, 55B, and 63B as well as thehose 64B) are formed in the measuring-head body portion 42. Themeasurement air is supplied to the measurement air nozzles 51A and 51Brespectively from the individual measurement supply passages. With theabove-described configuration, the measuring head 41 is capable ofmeasuring, not the inner diameter of the bush hole 31 a, but the gapsΔX1 and ΔX2 as well as ΔY1 and ΔY2 between the outer peripheral surface43 a of the measuring-head tip portion 43 and the inner peripheralsurface 31 b of the bush hole 31 a at both sides in the first radialdirection (the X-axis direction) and at both sides in the second radialdirection (the Y-axis direction) to each of which directions themeasuring-head tip portion 43 is perpendicular, by rotating themeasuring head 41 by 90 degrees by means of the main spindle 26.Accordingly, the amounts of eccentricity ΔX and ΔY between the mainspindle 26 and the bush hole 31 a are obtained on the basis of themeasured values of the gaps ΔX1 and ΔX2 as well as ΔY1 and ΔY2 (forexample, by calculation of the above-described equations (1) and (2)),and then, the position of the main spindle 26 is controlled inaccordance with the amounts of eccentricity ΔX and ΔY (that is, therelative position between the main spindle 26 and the bush hole 31 a iscorrected), whereby the axis of the main spindle 26 (the drilling tool32) and the axis of the bush hole 31 a are caused to coincide with eachother. Therefore, uneven wear of the bush hole 31 a can be prevented.

In addition, the measuring head 41 for an air micrometer of Embodiment 1is characterized by the following configuration. Specifically, themeasurement air is supplied from the first measurement air supplypassage 70A and the second measurement air supply passage 70A formed inthe main-spindle head 25, through the first measurement air supplypassage 68A and the second measurement air supply passage 68B in therotary joint 67 mounted on the measuring-head body portion 42, to thefirst measurement air supply passage 63A and the second measurement airsupply passage 63B in the measuring-head body portion 42, respectively.Accordingly, the following effect and the like can be obtained. Themeasurement air can be supplied from the main-spindle head 25, and thereis no need to connect such supply means as a hose for supplyingmeasurement air, directly to the measuring head 41. Therefore,operations for measurement, such as attachment and detachment of themeasuring head 41 to and from the main spindle 26, are facilitated.

Moreover, the measuring head 41 for an air micrometer of Embodiment 1 ischaracterized as follows. Specifically, in the measuring-head tipportion 43, the air-blow nozzles 52A to 52D are formed for jetting theair-blow air toward the inner peripheral surface 31 b of the bush hole31 a forward through the jetting openings 52A-1 to 52D-1 in the taperedsurface 49 on the peripheral edge of the distal end of themeasuring-head tip portion 43, at the time of measurement. In themeasuring-head body portion 42, the air-blow air supply passages 56 and65 are formed for supplying the air-blow air to the air-blow nozzles 52Ato 52D. Accordingly, even if foreign matter, such as a chip, is attachedonto the inner peripheral surface 31 b of the bush hole 31 a, it ispossible to perform the gap measurement after removing the foreignmatter from the inner peripheral surface 31 b of the bush hole 31 a withthe air blow, so that highly-precise gap measurement can be performed.

Further, the measuring head 41 for an air micrometer of Embodiment 1 ischaracterized as follows. Specifically, the air-blow air is suppliedfrom the air-blow air supply passage 73 formed in the main-spindle head25, through the air-blow air supply passage 72 in the rotary joint 71mounted on the main spindle 26 and the air-blow air supply passage 75formed in the main spindle 26, to the air-blow air supply passage 65 inthe measuring-head body portion 42. Accordingly, the following effectand the like can be obtained. The air-blow air can be supplied from themain-spindle head 25, and there is no need to connect supply means suchas a hose for supplying air-blow air, directly to the measuring head 41.Therefore, operations for measurement, such as attachment and detachmentof the measuring head 41 to and from the main spindle 26, arefacilitated.

Furthermore, the measuring head 41 for an air micrometer of Embodiment 1is characterized as follows. Specifically, the measuring-head bodyportion 42 includes: the distal-end-side member (the connection portion45 and the case 46) to which the measuring-head tip portion 43 is fixed;the proximal-end-side member 54; the coil spring 74 interposed betweenthe distal-end-side member (the connection portion 45 and the case 46)and the proximal-end-side member 54; and the flexible hoses 64A and 64Bconnecting the measurement air supply passages 55A and 55B formed in thedistal-end-side member (the case 46) and the measurement air supplypassages 63A and 63B in the proximal-end-side member 54 to each other,respectively. Accordingly, even if the measuring-head tip portion 43comes into contact with the bush 31 during the insertion of themeasuring-head tip portion 43 into the bush hole 31 a, the coil spring74 is compressed to cause the measuring-head tip portion 43 to movetoward the proximal end, so that the impact at the time of the contactis mitigated.

Embodiment 2

FIG. 9 is a side view of a measuring head for an air micrometeraccording to Embodiment 2 of the present invention. Part (a) of FIG. 10is a cross-sectional view showing part of the measuring head, Part (b)of FIG. 10 is a view in the direction of the arrow H in FIG. 9, Part (c)of FIG. 10 is a cross-sectional view taken along the line I-I in FIG. 9and viewed in the direction of the arrows I, Part (d) of FIG. 10 is across-sectional view taken along the line J-J in FIG. 9 and viewed inthe direction of the arrows J, Part (e) of FIG. 10 is a cross-sectionalview taken along the line K-K in FIG. 9 and viewed in the direction ofthe arrows K, and Part (f) of FIG. 10 is a cross-sectional view takenalong the line L-L in FIG. 9 and viewed in the direction of the arrowsL. FIG. 11 is a system configurational diagram of the air micrometer.FIG. 12 is a view in the direction of the arrow M in FIG. 11. FIG. 13 isa view showing how the measuring head is calibrated using anair-micrometer calibration device (similar to Part (b) of FIG. 8).

It should be noted that an example of a machined tool for which themeasuring head of Embodiment 2 is employed and a state where themeasuring head is mounted on a main spindle are similar to those shownin Part (a) of FIG. 1 and Part (b) of FIG. 1, respectively, andaccordingly will be neither illustrated in drawings nor described indetail herein. In addition, for the calibration of the measuring head ofEmbodiment 2, the air-micrometer calibration device 91 described inEmbodiment 1 is employed (see FIG. 7 and FIG. 8). Therefore, theair-micrometer calibration device will not be described in detailherein.

In the measuring head 41 of Embodiment 1, the two measurement airnozzles 51A and 51B are formed in the measuring-head tip portion 43 (seeFIG. 2 and FIG. 3). On the other hand, as shown in Part (b) of FIG. 10and Part (c) of FIG. 10, a measuring head 41 of Embodiment 2 ischaracterized in that four measurement air nozzles 51A, 51B, 51C, and51D are formed in a measuring-head tip portion 43, and the otherconfigurations are generally the same as those in Embodiment 1.Accordingly, in the measuring head 41 of Embodiment 2, the same parts asthose in Embodiment 1 will be given the same reference numerals, and thedetailed description that has already been made will be omitted.

As shown in FIG. 9 and Part (a) of FIG. 10 to Part (d) of FIG. 10, thefour measurement air nozzles 51A, 51B, 51C, and 51D are formed in themeasuring-head tip portion 43 of the measuring head 41 of Embodiment 2.Each of these measurement air nozzles 51A to 51D has an angle of 90degrees with respect to its adjacent ones in the circumferentialdirection of the measuring-head tip portion 43. In the measurement, themeasurement air nozzles 51A, 51B, 51C, and 51D jet air toward gapsbetween an outer peripheral surface 43 a of the measuring-head tipportion 43 and an inner peripheral surface 31 b of a bush hole 31 athrough jetting openings 51A-1, 51B-1, 51C-1, and 51D-1 in the outerperipheral surface 43 a. In addition, a first measurement air supplypassage 53A connected to the first measurement air nozzle 51A, a secondmeasurement air supply passage 53B connected to the second measurementair nozzle 51B, a third measurement air supply passage 53C connected tothe third measurement air nozzle 51C, and a fourth measurement airsupply passage 53D connected to the fourth measurement air nozzle 51Dare formed in a connection portion 45 of a measuring-head body portion42.

A first measurement air supply passage 55A, a second measurement airsupply passage 55B, a third measurement air supply passage 55C, and afourth measurement air supply passage 55D are formed in a wall portionof a case 46 of the measuring-head body portion 42. The firstmeasurement air supply passage 55A is connected to the aforementionedfirst measurement air supply passage 53A. The second measurement airsupply passage 55B is connected to the aforementioned second measurementair supply passage 53B. The third measurement air supply passage 55C isconnected to the aforementioned third measurement air supply passage53C. The fourth measurement air supply passage 55D is connected to theaforementioned fourth measurement air supply passage 53D.

A first measurement air supply passage 63A, a second measurement airsupply passage 63B, the first measurement air supply passage 63A, thesecond measurement air supply passage 63B, a third measurement airsupply passage 63C, and a fourth measurement air supply passage 63D areformed in a proximal-end-side member 54.

A first hose 64A, a second hose 64B, a third hose 64C, and a fourth hose64D which are flexible are wound around an outer peripheral surface of ashaft portion 60. The first hose 64A connects the first measurement airsupply passage 55A in the case 46 and the first measurement air supplypassage 63A in the proximal-end-side member 54 to each other. The secondhose 64B connects the second measurement air supply passage 55B in thecase 46 and the second measurement air supply passage 63A in theproximal-end-side member 54 to each other. The third hose 64C connectsthe third measurement air supply passage 55C in the case 46 and thethird measurement air supply passage 63C in the proximal-end-side member54 to each other. The fourth hose 64D connects the fourth measurementair supply passage 55D in the case 46 and the fourth measurement airsupply passage 63D in the proximal-end-side member 54 to each other.

Accordingly, the first measurement air nozzle 51A is supplied with themeasurement air through the first measurement air supply passage 63A,the first hose 64A, the first measurement air supply passage 55A, andthe first measurement air supply passage 53A. The second measurement airnozzle 51B is supplied with the measurement air through the secondmeasurement air supply passage 63B, the second hose 64B, the secondmeasurement air supply passage 55B, and the second measurement airsupply passage 53B. The third measurement air nozzle 51C is suppliedwith the measurement air through the third measurement air supplypassage 63C, the third hose 64C, the third measurement air supplypassage 55C, and the third measurement air supply passage 53C. Thefourth measurement air nozzle 51D is supplied with the measurement airthrough the fourth measurement air supply passage 63D, the fourth hose64D, the fourth measurement air supply passage 55D, and the fourthmeasurement air supply passage 53D.

It should be noted that, in Embodiment 2, no rotary joint is mounted onthe proximal-end-side member 54. The first measurement air supplypassage 63A in the proximal-end-side member 54 is connected to a firstmeasurement air supply passage 70A in the main-spindle head 25 through afirst coupler 69A, and the second measurement air supply passage 63B isconnected to a second measurement air supply passage 70B in themain-spindle head 25 through a second coupler 69B. Further, a thirdmeasurement air supply passage 63C is connected to a third measurementair supply passage (not illustrated) in the main-spindle head 25 througha third coupler (not illustrated), and a fourth measurement air supplypassage 63D is connected to a fourth measurement air supply passage (notillustrated) in the main-spindle head 25 through a fourth coupler (notillustrated). Accordingly, the first measurement air supply passage 63Ain the proximal-end-side member 54 is supplied with the measurement airfrom the first measurement air supply passage 70A in the main-spindlehead 25. The second measurement air supply passage 63B in theproximal-end-side member 54 is supplied with the measurement air fromthe second measurement air supply passage 70B in the main-spindle head25. The third measurement air supply passage 63C in theproximal-end-side member 54 is supplied with the measurement air fromthe third measurement air supply passage in the main-spindle head 25.The fourth measurement air supply passage 63D in the proximal-end-sidemember 54 is supplied with the measurement air from the fourthmeasurement air supply passage in the main-spindle head 25.

Next, the system configuration of the air micrometer and the proceduresof operation of gap measurement will be described on the basis of FIG.11, FIG. 12, and FIG. 6. It should be noted that the following operationis performed by controlling the operations of drive mechanisms of therespective axes, the rotation of a main-spindle motor, and the like, byuse of an NC system 78.

In the gap measurement, air blow is performed first. Since the air blowis the same as that in the case of Embodiment 1, the air blow will notbe described in detail. Thereafter, as shown in FIG. 11, themeasuring-head tip portion 43 inserted into the bush hole 31 a. Afterthat, a measurement instruction is outputted from the NC system 78 to asequencer 80, and then a measurement-direction selection instruction anda measurement start instruction are outputted from the sequencer 80 to acontrol device 81 of the air micrometer. As a result, the control on A/Dconverters 77A and 77B as well as air supply sources 76A and 76B by thecontrol device 81 is started, so that the gap measurement in the Y-axisdirection and the gap measurement in the X-axis direction are performed.Any of these gap measurements in the Y-axis direction and in the X-axisdirection may be performed first, or these gap measurements may beperformed at the same time. In Embodiment 2, since the four measurementair nozzles 51A to 51D are formed in the measuring-head tip portion 43,there is no need to rotate the measuring head 41 by 90 degrees as in thecase of Embodiment 1.

The gap measurement in the Y-axis direction will be described in detail.The measurement air with a pressure adjusted to be constant by pressureadjusting means such as a regulator is supplied, from the firstmeasurement air supply source 76A and the second measurement air supplysource 76B, through the first A/D converter 77A and the second A/Dconverter 77B, to the first measurement air nozzle 51A (the firstmeasurement air supply passage 70A in the main-spindle head 25) and thesecond measurement air nozzle 51B (the second measurement air supplypassage 70B in the main-spindle head 25) in the measuring-head tipportion 43, respectively. As a result, the measurement air is jettedfrom the first measurement air nozzle 51A and the second measurement airnozzle 51B respectively to gaps ΔY1 and ΔY2 each between the outerperipheral surface 43 a of the measuring-head tip portion 43 and theinner peripheral surface 31 b of the bush hole 31 a. In this event, thefirst A/D converter 77A and the second A/D converter 77B detect therespective pressures of the measurement air (which correspond to theflow rates of the measurement air), convert the detection signals intodigital signals, and output the digital signals to the control device81.

The control device 81 obtains the flow rates of the measurement air fromthe pressure detection signals outputted respectively from the first A/Dconverter 77A and the second A/D converter 77B, and then obtains the gapΔY1 and the gap ΔY2 on the basis of the data on the flow rates of themeasurement air and pre-stored data representing the relationshipbetween the flow rate of the measurement air and the gap, as shown inFIG. 6. Further, the control device 81 calculates an amount ofeccentricity ΔY between the main spindle 26 (the drilling tool 32) andthe bush hole 31 a in the Y-axis direction on the basis of the measuredvalues of the gaps ΔY1 and ΔY2 by the aforementioned equation (1), andoutputs the amount of eccentricity ΔY to the sequencer 80.

Next, the gap measurement in the X-axis direction will be described indetail. The measurement air with a pressure adjusted to be constant bythe pressure adjusting means such as a regulator is supplied, from athird measurement air supply source 76C and a fourth measurement airsupply source 76D, through a third A/D converter 77C and a fourth A/Dconverter 77D, to the third measurement air nozzle 51C (the thirdmeasurement air supply passage in the main-spindle head 25) and thefourth measurement air nozzle 51D (the fourth measurement air supplypassage in the main-spindle head 25) in the measuring-head tip portion43, respectively. As a result, the measurement air is jetted from thethird measurement air nozzle 51C and the fourth measurement air nozzle51D respectively to gaps ΔX1 and ΔX2 each between the outer peripheralsurface 43 a of the measuring-head tip portion 43 and the innerperipheral surface 31 b of the bush hole 31 a. In this event, the thirdA/D converter 77C and the fourth A/D converter 77D detect the respectivepressures of the measurement air (which correspond to the flow rates ofthe measurement air), convert the detection signals into digitalsignals, and output the digital signals to the control device 81.

The control device 81 obtains the flow rates of the measurement air fromthe pressure detection signals outputted respectively from the third A/Dconverter 77C and the fourth A/D converter 77D, and then obtains the gapΔX1 and the gap ΔX2 on the basis of the data on the flow rates of themeasurement air and pre-stored data representing the relationshipbetween the flow rate of the measurement air and the gap, as shown inFIG. 6. Further, the control device 81 calculates an amount ofeccentricity ΔX between the main spindle 26 (the drilling tool 32) andthe bush hole 31 a in the X-axis direction on the basis of the measuredvalues of the gaps ΔX1 and ΔX2 by the aforementioned equation (2), andoutputs the amount of eccentricity ΔX to the sequencer 80.

The sequencer 80 stores the amounts of eccentricity ΔX and ΔY receivedfrom the control device 81 into macro variables in the NC system 78.Then, the NC system 78 controls the position of the main spindle 26(that is, corrects the relative position between the main spindle 26 andthe bush hole 31 a) by shifting the X and Y coordinates of the mainspindle 26 in accordance with the amounts of eccentricity ΔX and ΔY. Inthis way, the NC system 78 causes the axis of the main spindle 26 (thedrilling tool 32) and the axis of the bush hole 31 a to coincide witheach other, thereby preventing uneven wear of the bush hole 31 a.

Also in Embodiment 2, the data representing the relationship between theflow rate of the measurement air and the gap, as shown in FIG. 6, isobtained by calibrating the air micrometer using the air-micrometercalibration device 91 described in Embodiment 1.

The procedures of calibration operation are also the same as those inthe case of Embodiment 1. The procedures of calibration operation willbe described on the basis of Part (a) of FIG. 8, FIG. 11, and FIG. 13.After the air blow is performed on the air-micrometer calibration device91 as described above (or without the air blow being performed), themeasuring-head tip portion 43 is first inserted into the small-diametermaster hole 95. At this time, the measuring-head body portion 42 (thecase 46) is located inside the clamping sleeve 93. Then, when oil issupplied from an unillustrated pressure oil supply source to thehydraulic pressure chamber 97 through the hose 99 and the pressure oilsupply passage 98, the hydraulic pressure in the hydraulic pressurechamber 97 acts on the entire clamping sleeve 93, causing the diameterof the clamping sleeve 93 to be slightly reduced, so that the clampingsleeve 93 clamps the measuring-head body portion 42 (the case 46). As aresult, the axis of the measuring-head tip portion 43 and the axis ofthe small-diameter master hole 95 are caused to coincide with eachother. To put it differently, a gap ΔG1 between the outer peripheralsurface 43 a of the measuring-head tip portion 43 and the innerperipheral surface 95 a of the small-diameter master hole 95 is madeuniform (a predetermined value) entirely in the circumferentialdirection of the measuring-head tip portion 43 as shown in FIG. 13.

In this state, as in the case of the gap measurement, the measurementair with a pressure adjusted to be constant by the pressure adjustingmeans such as a regulator is supplied, from the first measurement airsupply source 76A, the second measurement air supply source 76B, thethird measurement air supply source 76C, and the fourth measurement airsupply source 76D, through the first A/D converter 77A, the second A/Dconverter 77B, the third A/D converter 77C, and the fourth A/D converter77D, to the first measurement air nozzle 51A (the first measurement airsupply passage 70A in the main-spindle head 25), the second measurementair nozzle 51B (the second measurement air supply passage 70B in themain-spindle head 25), the third measurement air nozzle 51C (the thirdmeasurement air supply passage in the main-spindle head 25), and thefourth measurement air nozzle 51D (the third measurement air supplypassage in the main-spindle head 25) in the measuring-head tip portion43, respectively. As a result, these flows of the measurement air arejetted respectively from the first measurement air nozzle 51A, thesecond measurement air nozzle 51B, the third measurement air nozzle 51C,and the fourth measurement air nozzle 51D to the gap ΔG1 between theouter peripheral surface 43 a of the measuring-head tip portion 43 andthe inner peripheral surface 95 a of the small-diameter master hole 95.In this event, the first A/D converter 77A, the second A/D converter77B, the third A/D converter 77C, and the fourth A/D converter 77Ddetect the respective pressures of the measurement air (which correspondto the flow rates of the measurement air), convert the detection signalsinto digital signals, and output the digital signals to the controldevice 81, respectively.

Then, the control device 81 obtains the flow rate Q1 of the measurementair from the pressure detection signals outputted respectively from thefirst A/D converter 77A, the second A/D converter 77B, the third A/Dconverter 77C, and the fourth A/D converter 77D, and stores data on theflow rate Q1 of the measurement air and pre-stored data on the gap ΔG1as data of a point P1 representing the relationship between the flowrate Q1 of the measurement air and the gap ΔG1, as shown in FIG. 6.

Next, the pressure oil is discharged from the hydraulic pressure chamber97 through the pressure oil supply passage 98 and the hose 99, so thatthe clamping of the measuring-head body portion 42 (the case 46) by theclamping sleeve 93 is once released. After that, the measuring-head tipportion 43 is inserted into the large-diameter master hole 96. Also inthis case, the measuring-head body portion 42 (the case 46) is locatedinside the clamping sleeve 93. Then, in the same manner as describedabove, the oil is supplied from the pressure oil supply source to thehydraulic pressure chamber 97 through the hose 99 and the pressure oilsupply passage 98, so that the clamping sleeve 93 clamps themeasuring-head body portion 42 (the case 46) with the hydraulic pressurein the hydraulic pressure chamber 97. As a result, the axis of themeasuring-head tip portion 43 and the axis of the large-diameter masterhole 96 are caused to coincide with each other. To put it differently, agap ΔG2 between the outer peripheral surface 43 a of the measuring-headtip portion 43 and the inner peripheral surface 96 a of thelarge-diameter master hole 96 is made uniform (a predetermined value)entirely in the circumferential direction of the measuring-head tipportion 43 as shown in FIG. 13.

In this state, as in the case of the small-diameter master hole 95, themeasurement air with a pressure adjusted to be constant by the pressureadjusting means such as a regulator is supplied, from the firstmeasurement air supply source 76A, the second measurement air supplysource 76B, the third measurement air supply source 76C, and the fourthmeasurement air supply source 76D, through the first A/D converter 77A,the second A/D converter 77B, the third A/D converter 77C, and thefourth A/D converter 77D, to the first measurement air nozzle 51A (thefirst measurement air supply passage 70A in the main-spindle head 25),the second measurement air nozzle 51B (the second measurement air supplypassage 70B in the main-spindle head 25), the third measurement airnozzle 51C (the third measurement air supply passage in the main-spindlehead 25), and the fourth measurement air nozzle 51D (the fourthmeasurement air supply passage in the main-spindle head 25) in themeasuring-head tip portion 43, respectively. As a result, these flows ofthe measurement air are jetted respectively from the first measurementair nozzle 51A, the second measurement air nozzle 51B, the thirdmeasurement air nozzle 51C, and the fourth measurement air nozzle 51D tothe gap ΔG2 between the outer peripheral surface 43 a of themeasuring-head tip portion 43 and the inner peripheral surface 96 a ofthe large-diameter master hole 96. In this event, the first A/Dconverter 77A, the second A/D converter 77B, the third A/D converter77C, and the fourth A/D converter 77D detect the respective pressures ofthe measurement air (which correspond to the flow rates of themeasurement air), convert the detection signals into digital signals,and output the digital signals to the control device 81.

Then, the control device 81 obtains the flow rate Q2 of the measurementair from the pressure detection signals outputted respectively from thefirst A/D converter 77A, the second A/D converter 77B, the third A/Dconverter 77C, and the fourth A/D converter 77D, and stores data on theflow rate Q2 of the measurement air and pre-stored data on the gap ΔG2as data of a point P2 representing the relationship between the flowrate Q2 of the measurement air and the gap ΔG2, as shown in FIG. 6.Moreover, data between the point P2 and the aforementioned P1 isobtained by linear interpolation. Consequently, the data representingthe relationship between the flow rate of the measurement air and thegap as shown in FIG. 6 is obtained.

As described above, according to the measuring head 41 of Embodiment 2,provided is a measuring head 41 for an air micrometer configured to bemounted on the main spindle 26 of the machine tool 21 at the time ofmeasurement and inserted into the bush hole 31 a of the bush 31 attachedto the work table 23 of the machine tool 21, for measuring the amount ofeccentricity between the bush hole 31 a and the main spindle 26. Themeasuring head 41 for an air micrometer is characterized as follows.Specifically, the measuring head 41 includes: the measuring-head bodyportion 42; and the measuring-head tip portion 43 provided on the distalend of the measuring-head body portion 42 and configured to be insertedinto the bush hole 31 a at the time of the measurement. In addition, thefirst measurement air nozzle 51A, the second measurement air nozzle 51B,the third measurement air nozzle 510, and the fourth measurement airnozzle 51D are each formed to extend in the radial direction of themeasuring-head tip portion 43, and also each formed to have an angle of90 degrees with respect to its adjacent ones in the circumferentialdirection of the measuring-head tip portion 43. The first measurementair nozzle 51A, the second measurement air nozzle 51B, the thirdmeasurement air nozzle 51C, and the fourth measurement air nozzle 51Dare configured to blow measurement air to the gap between the outerperipheral surface 43 a of the measuring-head tip portion 43 and theinner peripheral surface 31 b of the bush hole 31 a respectively throughthe jetting openings 51A-1 to 51D-1 in the outer peripheral surface 43 aat the time of measurement. Moreover, the individual measurement airsupply passages corresponding to the respective measurement air nozzles51A to 51D (that is, the supply passage constituted of the firstmeasurement air supply passages 53A, 55A, and 63A as well as the hose64A, the supply passage constituted of the first measurement air supplypassages 53B, 55B, and 63B as well as the hose 64B, the supply passageconstituted of the third measurement air supply passages 53C, 55C, and63C as well as the hose 64C, and the supply passage constituted of thefourth measurement air supply passages 53D, 55D, and 63D as well as thehose 64D) are formed in the measuring-head body portion 42. Themeasurement air is supplied to the measurement air nozzles 51A to 51Drespectively from the individual measurement supply passages. With theabove-described configuration, the measuring head 41 is capable ofmeasuring, not the inner diameter of the bush hole 31 a, but the gapsΔX1 and ΔX2 as well as ΔY1 and ΔY2 between the outer peripheral surface43 a of the measuring-head tip portion 43 and the inner peripheralsurface 31 b of the bush hole 31 a at both sides in the first radialdirection (the X-axis direction) and at both sides in the second radialdirection (the Y-axis direction) to each of which directions themeasuring-head tip portion 43 is perpendicular. Accordingly, the amountsof eccentricity ΔX and ΔY between the main spindle 26 and the bush hole31 a are obtained on the basis of the measured values of the gaps ΔX1and ΔX2 as well as ΔY1 and ΔY2 (for example, by calculation of theabove-described equations (1) and (2)), and then, the position of themain spindle 26 is controlled in accordance with the amounts ofeccentricity ΔX and ΔY (that is, the relative position between the mainspindle 26 and the bush hole 31 a is corrected), whereby the axis of themain spindle 26 (the drilling tool 32) and the axis of the bush hole 31a are caused to coincide with each other. Therefore, uneven wear of thebush hole 31 a can be prevented.

In addition, the measuring head 41 for an air micrometer of Embodiment 2is characterized by the following configuration. Specifically, themeasurement air is supplied from the first measurement air supplypassage 70A, the second measurement air supply passage 70A, the thirdmeasurement air supply passage, and the fourth measurement air supplypassage formed in the main-spindle head 25 to the first measurement airsupply passage 63A, the second measurement air supply passage 63B, thethird measurement air supply passage 63C, and the fourth measurement airsupply passage 63D in the measuring-head body portion 42, respectively.Accordingly, the following effect and the like can be obtained. Themeasurement air can be supplied from the main-spindle head 25, and thereis no need to connect such supply means as a hose for supplyingmeasurement air directly to the measuring head 41. Therefore, operationsfor measurement, such as attachment and detachment of the measuring head41 to and from the main spindle 26, are facilitated.

Moreover, the measuring head 41 for an air micrometer of Embodiment 2 ischaracterized as follows. Specifically, in the measuring-head tipportion 43, the air-blow nozzles 52A to 52D are formed for jetting theair-blow air toward the inner peripheral surface 31 b of the bush hole31 a forward through the jetting openings 52A-1 to 52D-1 in the taperedsurface 49 on the peripheral edge of the distal end of themeasuring-head tip portion 43, at the time of measurement. In themeasuring-head body portion 42, the air-blow air supply passages 56 and65 are formed for supplying the air-blow air to the air-blow nozzles 52Ato 52D. Accordingly, even if foreign matter, such as a chip, is attachedonto the inner peripheral surface 31 b of the bush hole 31 a, it ispossible to perform the gap measurement after removing the foreignmatter from the inner peripheral surface 31 b of the bush hole 31 a withthe air blow, so that highly-precise gap measurement can be performed.

Further, the measuring head 41 for an air micrometer of Embodiment 2 ischaracterized as follows. Specifically, the air-blow air is suppliedfrom the air-blow air supply passage 73 formed in the main-spindle head25, through the air-blow air supply passage 72 in the rotary joint 71mounted on the main spindle 26 and the air-blow air supply passage 75formed in the main spindle 26, to the air-blow air supply passage 65 inthe measuring-head body portion 42. Accordingly, the following effectand the like can be obtained. The air-blow air can be supplied from themain-spindle head 25, and there is no need to connect supply means suchas a hose for supplying air-blow air, directly to the measuring head 41.Therefore, operations for measurement, such as attachment and detachmentof the measuring head 41 to and from the main spindle 26, arefacilitated.

Furthermore, the measuring head 41 for an air micrometer of Embodiment 2is characterized as follows. Specifically, the measuring-head bodyportion 42 includes: the distal-end-side member (the connection portion45 and the case 46) to which the measuring-head tip portion 43 is fixed;the proximal-end-side member 54; the coil spring 74 interposed betweenthe distal-end-side member (the connection portion 45 and the case 46)and the proximal-end-side member 54; and the flexible hoses 64A and 64Bconnecting the measurement air supply passages 55A and 55B formed in thedistal-end-side member (the case 46) and the measurement air supplypassages 63A and 63B in the proximal-end-side member 54 to each other,respectively. Accordingly, even if the measuring-head tip portion 43comes into contact with the bush 31 during the insertion of themeasuring-head tip portion 43 into the bush hole 31 a, the coil spring74 is compressed to cause the measuring-head tip portion 43 to movetoward the proximal end, so that the impact at the time of the contactis mitigated.

Embodiment 3

Part (a) of FIG. 14 is a side view of a main part of a measuring headfor an air micrometer according to Embodiment 3 of the presentinvention, Part (b) of FIG. 14 is a view in the direction of the arrow Nin Part (a) of FIG. 14, Part (c) of FIG. 14 is a cross-sectional viewtaken along the line O-O in Part (a) of FIG. 14 and viewed in thedirection of the arrows O, Part (d) of FIG. 14 is a cross-sectional viewtaken along the line P-P in Part (a) of FIG. 14 and viewed in thedirection of the arrows P, and Part (e) of FIG. 14 is a cross-sectionalview taken along the line Q-Q in Part (a) of FIG. 14 and viewed in thedirection of the arrows Q. FIG. 15 is a view showing how gap measurementis performed by the measuring head (similar to FIG. 5). FIG. 16 is aview showing how the measuring head is calibrated using anair-micrometer calibration device (similar to Part (b) of FIG. 8).Moreover, FIG. 17 shows a method of calculating an amount ofeccentricity. Part (a) of FIG. 17 is a view showing a state where ameasuring-head tip portion and a bush hole are not eccentric from eachother, Part (b) of FIG. 17 is a view showing a state where themeasuring-head tip portion is eccentric from the bush hole only in theX-axis direction, and Part (c) of FIG. 17 is a main-part enlarged viewof the state shown in Part (b) of FIG. 17.

It should be noted that an example of a machine tool for which themeasuring head of Embodiment 3 is employed and a state where themeasuring head is mounted on a main spindle are similar to those shownin Part (a) of FIG. 1 and Part (b) of FIG. 1, respectively, andaccordingly will be neither illustrated in drawings nor described indetail herein. In addition, for the calibration of the measuring head ofEmbodiment 3, the air-micrometer calibration device 91 described inEmbodiment 1 is employed (see FIG. 7 and FIG. 8). Therefore, theair-micrometer calibration device will not be described in detailherein. Moreover, in the measuring head of Embodiment 3, the same partsas those in Embodiment 1 will be given the same reference numerals, thedetailed description that has already been made will be omitted, and theillustration of the proximal end portion of the measuring-head bodyportion is omitted.

In the measuring head 41 of Embodiment 1, the first measurement airnozzle 51A and the second measurement air nozzle 51B formed in themeasuring-head tip portion 43 have an angle of 180 degrees with respectto each other in the circumferential direction of the measuring-head tipportion 43 (see FIG. 2 and FIG. 3). On the other hand, as shown in Part(a) of FIG. 14 to Part (d) of FIG. 14, a measuring head 41 of Embodiment3 is characterized in that a first measurement air nozzle 51A and asecond measurement air nozzle 51B formed in a measuring-head tip portion43 have an angle of 90 degrees with respect to each other in acircumferential direction of a measuring-head tip portion 43.Accordingly, measurement air supply passages and hoses in each part,such as measurement air supply passages 53A and 53B in a connectionportion 45 as well as measurement air supply passages 55A and 55B in acase 46, are also arranged in conformity with the arrangement of thefirst and second measurement air nozzles 51A and 51B.

The other part has the same configuration as that in Embodiment 1. Itshould be noted that, although not illustrated, no rotary joint ismounted on the measuring head 41 of Embodiment 3 as in the case of themeasuring head 41 of Embodiment 2 (see FIG. 9); therefore, Embodiment 3is different from Embodiment 1 in that the rotary joint 67 (the firstand second measurement air supply passages 68A and 68B) is notinterposed in the course of the supply passages for the measurement air.

In addition, although neither illustrated nor described in detail, thesystem configuration of an air micrometer and the procedures ofoperation of gap measurement are also the same as those of Embodiment 1(see FIG. 4). It should be noted, however, that, since the firstmeasurement air nozzle 51A and the second measurement air nozzle 51B arearranged to make an angle of 90 degrees with respect to each other asshown in FIG. 15, it is possible to measure the gap ΔY1 in the Y-axisdirection with the first measurement air nozzle 51A and to measure thegap ΔX1 in the X-axis direction with the second measurement air nozzle515, without rotating the measuring head 41. Therefore, Embodiment 3 isdifferent in this point from Embodiment 1.

In this case, a control device 81 (see FIG. 4) calculates the amounts ofeccentricity ΔX and ΔY by subtracting these measured values of the gapsΔX1 and ΔY1 from values of gaps which are stored in advance in thecontrol device 81, and which are those between the outer peripheralsurface 43 a of the measuring-head tip portion 43 and the innerperipheral surface 31 b of the bush hole 31 a at the time when there isno eccentricity. Specifically, the amounts of eccentricity ΔX and ΔY arecalculated by any one of a first eccentricity amount calculating methodand a second eccentricity amount calculating method which will bedescribed below.

(First Eccentricity Amount Calculating Method)

The first eccentricity amount calculating method is a method ofobtaining the amounts of eccentricity ΔX and ΔY by solving the followingsimultaneous equations (3) and (4):

ΔX=ΔX ₀ −ΔX1−R(1−cos(sin⁻¹(ΔY/R))  (3); and

ΔY=ΔY ₀ −ΔY1−R(1−cos(sin⁻¹(ΔX/R))  (4).

In the above-described equations (3) and (4), ΔX₀ and ΔY₀, representvalues of gaps in the X-axis direction and the Y-axis direction,respectively, which are inputted as initial values to the control device81 in advance, that is, values of gaps between the outer peripheralsurface 43 a of the measuring-head tip portion 43 and the innerperipheral surface 31 b of the bush hole 31 a at the time when there isno eccentricity. R represents the radius of the bush hole 31 a, which isinputted to the control device 81 in advance. It should be noted that itis also possible to input the radius r of the measuring-head tip portion43 to the control device 81 in advance, and then to calculate theinitial values ΔX₀ and ΔY₀ from the difference (R−r) between r and R.The gaps ΔX1 and ΔY1 are obtained, in the control device 81, byobtaining the flow rates of measurement air from pressure detectionsignals (digital signals) received from A/D converters 77A and 77B (seeFIG. 4), and then obtaining the gaps ΔX1 and ΔY1 on the basis of data onthe flow rates of the measurement air and pre-stored data representingthe relationship between the flow rate of measurement air and the gap,as in the case of Embodiment 1.

Detailed description will be given on the basis of FIG. 17. Consider acase where the value of gap in the Y-axis direction, which is measuredby the first measurement air nozzle 51A, is changed from the initialvalue ΔY₀ to the value ΔY1 because the measuring-head tip portion 43becomes eccentric only in the Y-axis direction by ΔY with respect to thebush hole 31 a as shown in Part (b) of FIG. 17 from the state where themeasuring-head tip portion 43 and the bush hole 31 a are not eccentricfrom each other as shown in Part (a) of FIG. 17. In this case, theamount of eccentricity ΔY in the Y-axis direction can be obtained by thefollowing equation (5):

ΔY=ΔY ₀ −ΔY1  (5).

However, although not actually becoming eccentric, the value of gap inthe X-axis direction, which is measured by the second measurement airnozzle 51B, changes by ΔX from the initial value to ΔX1 because of aninfluence of ΔY, as shown in Part (b) of FIG. 17. Accordingly, when theamount of change in gap ΔX′ in the X-axis direction due to the influenceof ΔY is taken into consideration, the amount of eccentricity ΔX in theX-axis direction can be obtained by the following equation (6). In thecase of Part (b) of FIG. 17, the amount of eccentricity ΔX is 0:

ΔX=ΔX ₀ −ΔX1−ΔX′  (6).

Then, as shown in Part (c) of FIG. 17, the amount of change ΔX′ can beobtained by the following equation (7). Therefore, the equation (3) canbe obtained by substituting the equation (7) into the equation (6):

$\begin{matrix}{{\Delta \; X^{\prime}} = {{R - {R\; \cos \; \theta}} = {R\left( {1 - {{\cos \left( {\sin^{- 1}\left( {\Delta \; {Y/R}} \right)} \right)}.}} \right.}}} & (7)\end{matrix}$

Although not described in detail, the same applies to the Y-axisdirection as in the case of the X-axis direction. With themeasuring-head tip portion 43 becoming eccentric only in the X-axisdirection by ΔX with respect to the bush hole 31 a, if the amount ofchange in gap ΔY′ in the Y-axis direction due to an influence of ΔX istaken into consideration, the amount of eccentricity ΔY in the Y-axisdirection can be obtained by the following equation (8):

ΔY=ΔY ₀ −ΔY1−ΔY′  (8).

Then, since the amount of change ΔY′ can be obtained by the followingequation (9), the equation (4) can be obtained by substituting theequation (9) into the equation (8):

$\begin{matrix}{{\Delta \; Y^{\prime}} = {{R - {R\; \cos \; \theta}} = {R\left( {1 - {{\cos \left( {\sin^{- 1}\left( {\Delta \; {X/R}} \right)} \right)}.}} \right.}}} & (9)\end{matrix}$

(Second Eccentricity Amount Calculating Method)

The second eccentricity amount calculating method is a method ofobtaining the amounts of eccentricity ΔX and ΔY by the followingequations (10) and (11) with the above-describe amounts of change ΔX′and ΔY′ not taken into consideration:

ΔX=ΔX ₀ −ΔX1  (10);

ΔY=ΔY ₀ −ΔY1  (11).

Since the amounts of eccentricity ΔX and ΔY are very much smaller thanthe radius R of the bush hole 31 a (ΔX, ΔY<<R), an influence of theamount of eccentricity in one direction out of the X-axis and Y-axisdirections on the measured value of gap in the other direction is small.For this reason, the amounts of change ΔX′ and ΔY′ can be ignored.Specifically, when ΔY<<R, ΔY/R≈0, and therefore, ΔX′≈0. On the otherhand, when ΔX<<R, ΔX/R≈0, and therefore, ΔY′≈0. For example, whenΔY=0.010 mm and R=10 mm, cos(sin(0.010/10))=0.9999995, andΔX′=10(1−0.9999995)=0.000005 m=0.005 μm. Consequently,ΔX′/ΔY=0.000005/0.010=0.0005=0.05%. Moreover, when ΔY=0.010 mm and R=5mm, ΔX′=0.00001 mm=0.01 μm. Consequently, ΔX′/ΔY=0.001=0.1%. Then, thesevalues 0.005 μm and 0.01 μm of the amounts of change ΔX′ aresufficiently smaller than the repeat measurement accuracy 1.5 μm of theair micrometer. The same applies to the amount of change ΔY′. Therefore,the amounts of change ΔX′ and ΔY′ can be ignored.

The calibration of the measuring head 41 in Embodiment 3 is the same asthat in the case of Embodiment 1. Specifically, the air-micrometercalibration device 91 described in Embodiment 1 is used to obtain datarepresenting the relationship between the gaps ΔG1 and ΔG2 as shown inFIG. 16 and the flow rates of measurement air (see FIG. 6).

As described above, according to the measuring head 41 of Embodiment 3,provided is a measuring head 41 for an air micrometer configured to bemounted on the main spindle 26 of the machine tool 21 at the time ofmeasurement and inserted into the bush hole 31 a of the bush 31 attachedto the work table 23 of the machine tool 21, for measuring the amount ofeccentricity between the bush hole 31 a and the main spindle 26. Themeasuring head 41 for an air micrometer is characterized as follows.Specifically, the measuring head 41 includes: the measuring-head bodyportion 42; and the measuring-head tip portion 43 provided on the distalend of the measuring-head body portion 42 and configured to be insertedinto the bush hole 31 a at the time of the measurement. In addition, thefirst measurement air nozzle 51A and the second measurement air nozzle51B are formed to extend in the radial direction of the measuring-headtip portion 43 and have an angle of 90 degrees with respect to eachother in the circumferential direction of the measuring-head tip portion43. The first measurement air nozzle 51A and the second measurement airnozzle 51B are configured to blow measurement air to the gap between theouter peripheral surface 43 a of the measuring-head tip portion 43 andthe inner peripheral surface 31 b of the bush hole 31 a respectivelythrough the jetting openings 51A-1 and 51B-1 in the outer peripheralsurface 43 a at the time of measurement. Moreover, the individualmeasurement air supply passages corresponding to the respectivemeasurement air nozzles 51A and 51B (that is, the supply passageconstituted of the first measurement air supply passages 53A, 55A, and63A as well as the hose 64A, and the supply passage constituted of thefirst measurement air supply passages 53B, 55B, and 63B as well as thehose 64B) are formed in the measuring-head body portion 42. Themeasurement air is supplied to the measurement air nozzles 51A and 51Brespectively from the individual measurement supply passages. With theabove-described configuration, the measuring head 41 is capable ofmeasuring, not the inner diameter of the bush hole 31 a, but the gapsΔX1 and ΔY1 between the outer peripheral surface 43 a of themeasuring-head tip portion 43 and the inner peripheral surface 31 b ofthe bush hole 31 a in the first radial direction (the X-axis direction)and the second radial direction (the Y-axis direction) to each of whichdirections the measuring-head tip portion 43 is perpendicular.Accordingly, the amounts of eccentricity ΔX and ΔY between the mainspindle 26 and the bush hole 31 a are obtained on the basis of themeasured values of the gaps ΔX1 and ΔY1 (for example, by subtracting themeasured values of the gaps ΔX1 and ΔY1 from values of gaps between theouter peripheral surface of the measuring-head tip portion and the innerperipheral surface of the bush hole at the time when there is noeccentricity), and then, the position of the main spindle 26 iscontrolled in accordance with the amounts of eccentricity ΔX and ΔY(that is, the relative position between the main spindle 26 and the bushhole 31 a is corrected), whereby the axis of the main spindle 26 (thedrilling tool 32) and the axis of the bush hole 31 a are caused tocoincide with each other. Therefore, uneven wear of the bush hole 31 acan be prevented.

In addition, the measuring head 41 for an air micrometer of Embodiment 3is characterized by the following configuration. Specifically, themeasurement air is supplied from the first measurement air supplypassage 70A and the second measurement air supply passage 70A formed inthe main-spindle head 25 to the first measurement air supply passage 63Aand the second measurement air supply passage 63B in the measuring-headbody portion 42, respectively. Accordingly, the following effect and thelike can be obtained. The measurement air can be supplied from themain-spindle head 25, and there is no need to connect such supply meansas a hose for supplying measurement air, directly to the measuring head41. Therefore, operations for measurement, such as attachment anddetachment of the measuring head 41 to and from the main spindle 26, arefacilitated.

Moreover, the measuring head 41 for an air micrometer of Embodiment 3 ischaracterized as follows. Specifically, in the measuring-head tipportion 43, the air-blow nozzles 52A to 52D are formed for jetting theair-blow air toward the inner peripheral surface 31 b of the bush hole31 a forward through the jetting openings 52A-1 to 52D-1 in the taperedsurface 49 on the peripheral edge of the distal end of themeasuring-head tip portion 43, at the time of measurement. In themeasuring-head body portion 42, the air-blow air supply passages 56 and65 are formed for supplying the air-blow air to the air-blow nozzles 52Ato 52D. Accordingly, even if foreign matter, such as a chip, is attachedonto the inner peripheral surface 31 b of the bush hole 31 a, it ispossible to perform the gap measurement after removing the foreignmatter from the inner peripheral surface 31 b of the bush hole 31 a withthe air blow, so that highly-precise gap measurement can be performed.

Further, the measuring head 41 for an air micrometer of Embodiment 3 ischaracterized as follows. Specifically, the air-blow air is suppliedfrom the air-blow air supply passage 73 formed in the main-spindle head25, through the air-blow air supply passage 72 in the rotary joint 71mounted on the main spindle 26 and the air-blow air supply passage 75formed in the main spindle 26, to the air-blow air supply passage 65 inthe measuring-head body portion 42. Accordingly, the following effectand the like can be obtained. The air-blow air can be supplied from themain-spindle head 25, and there is no need to connect supply means suchas a hose for supplying air-blow air, directly to the measuring head 41.Therefore, operations for measurement, such as attachment and detachmentof the measuring head 41 to and from the main spindle 26, arefacilitated.

Furthermore, the measuring head 41 for an air micrometer of Embodiment 3is characterized as follows. Specifically, the measuring-head bodyportion 42 includes: the distal-end-side member (the connection portion45 and the case 46) to which the measuring-head tip portion 43 is fixed;the proximal-end-side member 54; the coil spring 74 interposed betweenthe distal-end-side member (the connection portion 45 and the case 46)and the proximal-end-side member 54; and the flexible hoses 64A and 64Bconnecting the measurement air supply passages 55A and 55B formed in thedistal-end-side member (the case 46) and the measurement air supplypassages 63A and 63B in the proximal-end-side member 54 to each other,respectively. Accordingly, even if the measuring-head tip portion 43comes into contact with the bush 31 during the insertion of themeasuring-head tip portion 43 into the bush hole 31 a, the coil spring74 is compressed to cause the measuring-head tip portion 43 to movetoward the proximal end, so that the impact at the time of the contactis mitigated.

Embodiment 4

Part (a) of FIG. 18 is a side view of a main part of a measuring headfor an air micrometer according to Embodiment 4 of the presentinvention, Part (b) of FIG. 18 is a view in the direction of the arrow Rin Part (a) of FIG. 18, Part (c) of FIG. 18 is a cross-sectional viewtaken along the line S-S in Part (a) of FIG. 18 and viewed in thedirection of the arrows S, and Part (d) of FIG. 18 is a cross-sectionalview taken along the line V-V in Part (a) of FIG. 18 and viewed in thedirection of the arrow V. Part (a) of FIG. 19 is a view showing how gapmeasurement is performed by the measuring head (similar to FIG. 5), andPart (b) of FIG. 19 is a view showing a state where the measuring headis rotated by 90 degrees from the state shown in Part (a) of FIG. 19(similar to FIG. 5). FIG. 20 is a view showing how the measuring head iscalibrated using the air-micrometer calibration device (similar to Part(b) of FIG. 8).

It should be noted that an example of a machined tool for which themeasuring head of Embodiment 4 is employed and a state where themeasuring head is mounted on a main spindle are similar to those shownin Part (a) of FIG. 1 and Part (b) of FIG. 1, respectively, andaccordingly will be neither illustrated in drawings nor described indetail herein. In addition, for the calibration of the measuring head ofEmbodiment 4, the air-micrometer calibration device 91 described inEmbodiment 1 is employed (see FIG. 7 and FIG. 8). Therefore, theair-micrometer calibration device will not be described in detailherein. Moreover, in the measuring head of Embodiment 4, the same partsas those in Embodiment 1 will be given the same reference numerals, thedetailed description that has already been made will be omitted, and theillustration of the proximal end portion of the measuring-head bodyportion is omitted.

In the measuring head 41 of Embodiment 1, the two measurement airnozzles 51A and 51B are formed in the measuring-head tip portion 43 (seeFIG. 2 and FIG. 3). On the other hand, a measuring head 41 of Embodiment4 is characterized in that only a single measurement air nozzle 51A isformed in a measuring-head tip portion 43, as shown in Part (a) of FIG.18 to Part (d) of FIG. 18. Accordingly, the number of measurement airsupply passages and the number of hoses in each part, such as a singlemeasurement air supply passage 53A in a connection portion 45 as well asa single measurement air supply passage 55A in a case 46, is one each.The other part has the same configuration as that in Embodiment 1.

In addition, although neither illustrated nor described in detail, thesystem configuration of an air micrometer and the procedures ofoperation of gap measurement are also the same as those of Embodiment 1(see FIG. 4). It should be noted, however, that, since only the singlemeasurement air nozzle 51A is formed in the measuring-head tip portion43, only a single measurement air supply source and a single A/Dconverter are provided accordingly. Therefore, Embodiment 4 is differentin this point from Embodiment 1.

Moreover, when the gap measurement is performed, the gap ΔY1 in theY-axis direction is measured in the state shown in Part (a) of FIG. 19.Subsequently, the measuring head 41 (the measuring-head tip portion 43)is rotated by 90 degrees by the control on a main spindle 26 (see FIG. 1and FIG. 2) by a NC system 78 (see FIG. 4), whereby the gap ΔX1 in theX-axis direction is measured, as shown in Part (a) of FIG. 19.

Also in this case, as in the case of Embodiment 3, a control device 81(see FIG. 4) calculates the amounts of eccentricity ΔX and ΔY bysubtracting these measured values of the gaps ΔX1 and ΔY1 from values ofgaps which are stored in advance in the control device 81, and which arethose between an outer peripheral surface 43 a of a measuring-head tipportion 43 and an inner peripheral surface 31 b of a bush hole 31 a atthe time when there is no eccentricity. Specifically, as in the case ofEmbodiment 3, the amounts of eccentricity ΔX and ΔY are calculated byany one of the first eccentricity amount calculating method and thesecond eccentricity amount calculating method described above.

The calibration of the measuring head 41 in Embodiment 4 is the same asthat in the case of Embodiment 1. Specifically, the air-micrometercalibration device 91 described in Embodiment 1 is used to obtain datarepresenting the relationship between the gaps ΔG1 and ΔG2 as shown inFIG. 20 and the flow rates of measurement air (see FIG. 6).

As described above, according to the measuring head 41 of Embodiment 4,provided is a measuring head 41 for an air micrometer configured to bemounted on the main spindle 26 of the machine tool 21 at the time ofmeasurement and inserted into the bush hole 31 a of the bush 31 attachedto the work table 23 of the machine tool 21, for measuring the amount ofeccentricity between the bush hole 31 a and the main spindle 26. Themeasuring head 41 for an air micrometer is characterized as follows.Specifically, the measuring head 41 includes: the measuring-head bodyportion 42; and the measuring-head tip portion 43 provided on the distalend of the measuring-head body portion 42 and configured to be insertedinto the bush hole 31 a at the time of the measurement. In addition, thesingle measurement air nozzle 51A is formed to extend in the radialdirection of the measuring-head tip portion 43. The first measurementair nozzle 51A is configured to blow measurement air to the gap betweenthe outer peripheral surface 43 a of the measuring-head tip portion 43and the inner peripheral surface 31 b of the bush hole 31 a through thejetting opening 51A-1 in the outer peripheral surface 43 a at the timeof measurement. Moreover, the single measurement air supply passagecorresponding to the measurement air nozzle 51A (that is, the supplypassage constituted of the first measurement air supply passages 53A,55A, and 63A as well as the hose 64A) is formed in the measuring-headbody portion 42. The measurement air is supplied to the singlemeasurement air nozzle 51A from the single measurement supply passage.With the above-described configuration, the measuring head 41 is capableof measuring, not the inner diameter of the bush hole 31 a, but the gapsΔX1 and ΔY1 between the outer peripheral surface 43 a of themeasuring-head tip portion 43 and the inner peripheral surface 31 b ofthe bush hole 31 a in the first radial direction (the X-axis direction)and the second radial direction (the Y-axis direction) to each of whichdirections the measuring-head tip portion 43 is perpendicular, byrotating the measuring head 41 by 90 degrees by means of the mainspindle 26, for example. Accordingly, the amounts of eccentricity ΔX andΔY between the main spindle 26 and the bush hole 31 a are obtained onthe basis of the measured values of the gaps ΔX1 and ΔY1 (for example,by subtracting the measured values of the gaps ΔX1 and ΔY1 from valuesof gaps between the outer peripheral surface of the measuring-head tipportion and the inner peripheral surface of the bush hole at the timewhen there is no eccentricity), and then, the position of the mainspindle 26 is controlled in accordance with the amounts of eccentricityΔX and ΔY (that is, the relative position between the main spindle 26and the bush hole 31 a is corrected), whereby the axis of the mainspindle 26 (the drilling tool 32) and the axis of the bush hole 31 a arecaused to coincide with each other. Therefore, uneven wear of the bushhole 31 a can be prevented.

In addition, the measuring head 41 for an air micrometer of Embodiment 4is characterized by the following configuration. Specifically, themeasurement air is supplied from the measurement air supply passage 70Aformed in the main-spindle head 25, through the measurement air supplypassage 68A in the rotary joint 67 mounted on the measuring-head bodyportion 42, to the first measurement air supply passage 63A in themeasuring-head body portion 42. Accordingly, the following effect andthe like can be obtained. The measurement air can be supplied from themain-spindle head 25, and there is no need to connect such supply meansas a hose for supplying measurement air, directly to the measuring head41. Therefore, operations for measurement, such as attachment anddetachment of the measuring head 41 to and from the main spindle 26, arefacilitated.

Moreover, the measuring head 41 for an air micrometer of Embodiment 4 ischaracterized as follows. Specifically, in the measuring-head tipportion 43, the air-blow nozzles 52A to 52D are formed for jetting theair-blow air toward the inner peripheral surface 31 b of the bush hole31 a forward through the jetting openings 52A-1 to 52D-1 in the taperedsurface 49 on the peripheral edge of the distal end of themeasuring-head tip portion 43, at the time of measurement. In themeasuring-head body portion 42, the air-blow air supply passages 56 and65 are formed for supplying the air-blow air to the air-blow nozzles 52Ato 52D. Accordingly, even if foreign matter, such as a chip, is attachedonto the inner peripheral surface 31 b of the bush hole 31 a, it ispossible to perform the gap measurement after removing the foreignmatter from the inner peripheral surface 31 b of the bush hole 31 a withthe air blow, so that highly-precise gap measurement can be performed.

Further, the measuring head 41 for an air micrometer of Embodiment 4 ischaracterized as follows. Specifically, the air-blow air is suppliedfrom the air-blow air supply passage 73 formed in the main-spindle head25, through the air-blow air supply passage 72 in the rotary joint 71mounted on the main spindle 26 and the air-blow air supply passage 75formed in the main spindle 26, to the air-blow air supply passage 65 inthe measuring-head body portion 42. Accordingly, the following effectand the like can be obtained. The air-blow air can be supplied from themain-spindle head 25, and there is no need to connect supply means suchas a hose for supplying air-blow air, directly to the measuring head 41.Therefore, operations for measurement, such as attachment and detachmentof the measuring head 41 to and from the main spindle 26, arefacilitated.

Furthermore, the measuring head 41 for an air micrometer of Embodiment 4is characterized as follows. Specifically, the measuring-head bodyportion 42 includes: the distal-end-side member (the connection portion45 and the case 46) to which the measuring-head tip portion 43 is fixed;the proximal-end-side member 54; the coil spring 74 interposed betweenthe distal-end-side member (the connection portion 45 and the case 46)and the proximal-end-side member 54; and the flexible hose 64Aconnecting the measurement air supply passages 55A and 55B formed in thedistal-end-side member (the case 46) and the measurement air supplypassages 63A and 63B in the proximal-end-side member 54 to each other,respectively. Accordingly, even if the measuring-head tip portion 43comes into contact with the bush 31 during the insertion of themeasuring-head tip portion 43 into the bush hole 31 a, the coil spring74 is compressed to cause the measuring-head tip portion 43 to movetoward the proximal end, so that the impact at the time of the contactis mitigated.

It should be noted that, a rotary joint for supplying measurement airmay be provided in the main spindle so that not only the blow air butalso the measurement air would be supplied to the measurement air supplypassage in the measuring head through a measurement air supply passagein the rotary joint and the measurement air supply passage in the mainspindle.

Moreover, the supply of the air-blow air is not limited to the casewhere the air-blow air is supplied from the air-blow air supply passagein the main-spindle head, through the air-blow air supply passage in therotary joint and the air-blow air supply passage in the main spindle, tothe air-blow air supply passage in the measuring head, as describedabove. The air-blow air may be configured to be supplied from anair-blow air supply passage in a main-spindle head, directly or throughan air-blow air supply passage in a rotary joint mounted on a measuringhead, to an air-blow air supply passage in the measuring head.

INDUSTRIAL APPLICABILITY

The present invention relates to a measuring head for an air micrometer,and is useful when applied to a case where the amount of eccentricitybetween a bush hole and a main spindle (a drilling tool) in a machinetool.

1. A measuring head for an air micrometer, the measuring head configuredto be mounted on a main spindle of a machine tool at the time ofmeasurement and inserted into a bush hole of a bush attached to a worktable of the machine tool, for measuring an amount of eccentricitybetween the bush hole and the main spindle, the measuring headcharacterized by comprising: a measuring-head body portion; and ameasuring-head tip portion provided on a distal end of themeasuring-head body portion, and configured to be inserted into the bushhole at the time of the measurement, the measuring head characterized inthat one or a plurality of measurement air nozzles are formed in themeasuring-head tip portion, the measurement air nozzles configured toblow measurement air to a gap between an outer peripheral surface of themeasuring-head tip portion and an inner peripheral surface of the bushhole respectively through jetting openings in the outer peripheralsurface at the time of measurement, individual measurement air supplypassages corresponding to the respective measurement air nozzles areformed in the measurement-head body portion, and the measurement air issupplied to the measurement air nozzles respectively through theindividual measurement air supply passages.
 2. The measuring head for anair micrometer, according to claim 1, characterized in that themeasurement air nozzles are a first measurement air nozzle and a secondmeasurement air nozzle each of which is formed to extend in a radialdirection of the measuring-head tip portion, and which have an angle of180 degrees with respect to each other in a circumferential direction ofthe measuring-head tip portion, and the measurement air supply passagesare a first measurement air supply passage for supplying the measurementair to the first measurement air nozzle and a second measurement airsupply passage for supplying the measurement air to the secondmeasurement air nozzle.
 3. The measuring head for an air micrometer,according to claim 1, characterized in that the measurement air nozzlesare a first measurement air nozzle, a second measurement air nozzle, athird measurement air nozzle, and a fourth measurement air nozzle eachof which is formed to extend in a radial direction of the measuring-headtip portion, and each of which has an angle of 90 degrees with respectto its adjacent ones in a circumferential direction of themeasuring-head tip portion, and the measurement air supply passages area first measurement air supply passage for supplying the measurement airto the first measurement air nozzle, a second measurement air supplypassage for supplying the measurement air to the second measurement airnozzle, a third measurement air supply passage for supplying themeasurement air to the third measurement air nozzle and a fourthmeasurement air supply passage for supplying the measurement air to thefourth measurement air nozzle.
 4. The measuring head for an airmicrometer, according to claim 1, characterized in that the measurementair nozzles are a first measurement air nozzle and a second measurementair nozzle each of which is formed to extend in a radial direction ofthe measuring-head tip portion, and which have an angle of 90 degreeswith respect to each other in a circumferential direction of themeasuring-head tip portion, and the measurement air supply passages area first measurement air supply passage for supplying the measurement airto the first measurement air nozzle and a second measurement air supplypassage for supplying the measurement air to the second measurement airnozzle.
 5. The measuring head for an air micrometer, according to claim1, characterized in that the measurement air nozzles are a singlemeasurement air nozzle formed to extend in a radial direction of themeasuring-head tip portion, and the measurement air supply passages area single measurement air supply passage for supplying the measurementair to the single measurement air nozzle.
 6. The measuring head for anair micrometer, according to claim 2, characterized in that themeasurement air is supplied from a first measurement air supply passageand a second measurement air supply passage that are formed in a supportportion of the main spindle, through a first measurement air supplypassage and a second measurement air supply passage in a rotary jointmounted on the measuring-head body portion, to the first measurement airsupply passage and the second measurement air supply passage in themeasuring-head body portion, respectively, or the measurement air issupplied from a first measurement air supply passage and a secondmeasurement air supply passage that are formed in a support portion ofthe main spindle, through a first measurement air supply passage and asecond measurement air supply passage in a rotary joint mounted on themain spindle as well as a first measurement air supply passage and asecond measurement air supply passage that are formed in the mainspindle, to the first measurement air supply passage and the secondmeasurement air supply passage in the measuring-head body portion,respectively.
 7. The measuring head for an air micrometer, according toclaim 5, characterized in that the measurement air is supplied from ameasurement air supply passage that is formed in a support portion ofthe main spindle, through a measurement air supply passage in a rotaryjoint mounted on the measuring-head body portion, to the measurement airsupply passage in the measuring head body portion, or the measurementair is supplied from a measurement air supply passage that is formed ina support portion of the main spindle, through a measurement air supplypassage in a rotary joint mounted on the main spindle as well as ameasurement air supply passage that is formed in the main spindle, tothe measurement air supply passage in the measuring head body portion.8. The measuring head for an air micrometer, according to claim 3,characterized in that the measurement air is supplied from a firstmeasurement air supply passage, a second measurement air supply passage,a third measurement air supply passage, and a fourth measurement airsupply passage that are formed in a support portion of the main spindle,to the first measurement air supply passage, the second measurement airsupply passage, the third measurement air supply passage, and the fourthmeasurement air supply passage in the measuring-head body portion,respectively.
 9. The measuring head for an air micrometer, according toclaim 4, characterized in that the measurement air is supplied from afirst measurement air supply passage and a second measurement air supplypassage that are formed in a support portion of the main spindle, to thefirst measurement air supply passage and the second measurement airsupply passage in the measuring-head body portion, respectively.
 10. Themeasuring head for an air micrometer, according to claim 1,characterized in that an air-blow nozzle is formed in the measuring-headtip portion, the air-blow nozzle configured to jet air-blow air towardthe inner peripheral surface of the bush hole forward through a jettingopening in a tapered surface on a peripheral edge of a distal end of themeasuring-head tip portion, at the time of measurement and an air-blowair supply passage for supplying the air-blow air to the air-blow nozzleis formed in the measuring-head body portion.
 11. The measuring head foran air micrometer, according to claim 10, characterized in that theair-blow air is supplied from an air-blow air supply passage that isformed in a support portion of the main spindle, to the air-blow airsupply passage in the measuring-head body portion, directly or throughan air-blow air supply passage in a rotary joint mounted on the mainspindle as well as an air-blow air supply passage that is formed in themain spindle.
 12. The measuring head for an air micrometer, according toclaim 1, characterized in that the measuring-head body portion includes:a distal-end-side member to which the measuring-head tip portion isfixed; a proximal-end-side member; an elastic member interposed betweenthe distal-end-side member and the proximal-end-side member; and aflexible hose connecting a measurement air supply passage that is formedin the distal-end-side member and a measurement air supply passage thatis formed in the proximal-end-side member to each other.